Mechanisms resulting in abdominal pain include altered neuro-immune interactions in the gastrointestinal tract, but the signaling processes that link immune activation with visceral hypersensitivity are unresolved. We hypothesized that enteric glia link the neural and immune systems of the gut and that communication between enteric glia and immune cells modulates the development of visceral hypersensitivity. To this end, we manipulated a major mechanism of glial intercellular communication that requires connexin-43 and assessed the effects on acute and chronic inflammation, visceral hypersensitivity, and immune responses. Deleting connexin-43 in glia protected against the development of visceral hypersensitivity following chronic colitis. Mechanistically, the protective effects of glial manipulation were mediated by disrupting the glial-mediated activation of macrophages through the macrophage colony-stimulating factor. Collectively, our data identified enteric glia as a critical link between gastrointestinal neural and immune systems that could be harnessed by therapies to ameliorate abdominal pain.

Background: Dietary sodium (Na) and central adiposity are considered important risk factors for hypertension (HTN). Blood pressure (BP) levels are discordant among 40-50% of monozygotic (MZ) twin pairs. One prior study of MZ twins using questionnaires reported that hypertensive (HT) MZ twins differed in their intake of meat and milk. However, none of the previous studies have evaluated the impact of Na intake on BP in MZ twins. Methods: Eighty-eight pairs of MZ twins were enrolled from Milwaukee, WI and Michigan State University Twin Registry, East Lansing, MI (age- 44 ± 9 years, 63% women, and 96% Caucasian). BPs (measured in triplicate and averaged) and anthropometrics were measured. Na intake was calculated using Block Sodium Screener. Twin pairs were considered concordant or discordant based on systolic (SBP) or diastolic BP (DBP) difference of 10 mm Hg between co-twins, off BP medications Results: Thirty-seven twin pairs were discordant in their BP levels. Mean (± SD, mm Hg) SBP/DBPs among concordant and discordant twins were 120 ± 12 / 77 ± 9 and 131 ± 18 / 81 ± 10 respectively. Mean differences in SBP/DBP among concordant and discordant twins were 5 ± 7 / 4 ± 4 and 14 ± 8 / 10 ± 6 respectively. Discordant twins as a group had higher waist circumference (WC) compared to concordant twins (p<0.05), but with no differences in BMI or Na intake. However, among the discordant twin pairs, the co-twin with higher BPs (138 ± 18 / 85 ± 9) had higher dietary salt intakes (3900 ± 1437 vs. 3261 ± 1058 mg/d) and higher WC (105 ± 15 vs. 98 ± 18 cm) (p=0.02) compared to their co-twin with lower BPs (121 ± 16 / 77 ± 9). The average Na intake among the concordant twins was 3443 ± 1189 mg/day. Differences in Na intake among discordant co-twins remained statistically significant after adjustment for age, gender, BMI, WC, and waist-to-hip ratio. Conclusions: Higher Na intake is associated with higher BPs among MZ twins with discordant BPs. Differences in Na intakes were significant independent of central adiposity indicating significant Na sensitivity in discordant MZ twin pairs. The effect of ~500mg less Na intake/day in resulting in lower BPs in genetically identical individuals, suggests that modest decreases in Na-intake in Na-sensitive individuals may be sufficient to see the desired effect on BP levels.

Introduction In obese humans, inflammation and adipokine production affect mortality and cardiovascular tissue remodeling independent of BMI. Studies of plasma adipokine levels suggest that anti‐inflammatory adipokines including omentin‐1, secreted frizzled‐related protein 5 (SFRP5), and adiponectin improve cardiovascular function while pro‐inflammatory adipokines, like resistin, impair cardiovascular function. Furthermore, adipokine production and function differ in males and females. Therefore, we tested the hypothesis that in human obesity, the degree of vascular/perivascular pathology is sex‐dependent and associated with a distinct adipokine profile. Methods Mesenteric vessels and perivascular adipose tissue were obtained from 26 obese patients (4 males, 22 females) undergoing Roux‐en‐Y bariatric surgery. A blinded semi‐quantitative approach was used to assess 4 criteria: Fibrosis, adventitial wall thickening, angiogenesis, and immune cell infiltration. Samples with 2+ criteria were considered abnormal (pathology). Expression levels of adiponectin, omentin‐1, resistin, and SFRP5 in perivascular fat (PVAT) were evaluated by qRT‐PCR. All collected data were analyzed by histopathology and sex. Results 60% of female tissue samples displayed significant pathology, which consistently involved fibrosis and adventitial wall thickening. Significant pathology was not observed in male tissues. When categorized by histopathology alone, females with pathology had 3‐fold lower omentin‐1 mRNA and 2‐fold higher resistin mRNA vs. females and males without pathology. When compared to males, females without pathology had 10‐fold higher omentin‐1 mRNA whereas obese females with pathology had only 1.6‐fold higher omentin‐1 mRNA and 1.6‐fold higher resistin mRNA. In females only, females with pathology had 5‐fold lower omentin‐1 mRNA, 2‐fold higher resistin mRNA and 2‐fold higher SFRP5 mRNA vs. females without pathology. None of these findings were associated with age, BMI, type II diabetes, dyslipidemia, or hypertension. Conclusions In the mesentery, females are more susceptible to obesity‐associated vascular/perivascular tissue remodeling than males. When compared to obese females without pathology, obese females with pathology have lower omentin‐1 mRNA and higher mRNA levels of resistin and SFRP5. Therefore, omentin‐1, resistin and SFRP5 may be useful adipokines in identifying obese females at risk of worsening cardiovascular tissue quality. Support or Funding Information Supported by NIH 2P01HL070687

Background: Genetic factors determining blood pressure (BP) are largely unmodifiable. Understanding the effects of physiologic, environmental, and epigenetic (modifiable) factors on BP levels can improve strategies for hypertension (HTN) control. Monozygotic (MZ) twins with identical genetic background are a good model to study the effect of these factors on BP. Methods: Seventy pairs of MZ twins were from Milwaukee, WI and Michigan State University Twin Registry, East Lansing, MI (62% women; age of 44 ± 10 years). BPs (measured in triplicate and averaged), anthropometrics, physical activity (Rapid Assessment of Physical Activity), and sodium intake measurements (Block Sodium Screener) were obtained. DNA was obtained from T-lymphocytes for methylation (epigenetic) sequencing analysis. Differences in systolic (SBP) and diastolic (DBP) BPs between co-twins were used as continuous variables for these analyses. Results: Mean SBP was 124 ± 15 mm Hg (mean ± SD) and DBP was 78 ± 11 mm Hg. Average differences in SBP and DBP among co-twins were 8 ± 9 and 7 ± 6 mm Hg respectively. Twin pairs were considered concordant or discordant based on BP difference of 10 mm Hg between co-twins or one twin being hypertensive. Discordant twins as a group had higher BMI and waist circumference (WC) compared to concordant twins (p<0.05). Among discordant twins, the co-twin with higher BPs tended to have higher waist circumference (WC) (105 ± 15 vs. 98 ± 18 cm) and dietary salt intake (3900 ± 1437 vs. 3261 ± 1058 mg/d) even though they did not reach statistical significance. There were no differences in physical activity or education levels. Genome-wide methylation analyses revealed that 3 loci were associated with SBP difference and 2 were associated with DBP difference at an unadjusted significance level of p < 10 -4 . Two sites reached an adjusted significance level of 0.08 with SBP difference. Conclusions: In this study, we identified several differentially methylated sites of interest in relation to BP among MZ twins. In addition, higher central adiposity and sodium intake may contribute to BP levels among MZ twins. Understanding the relationship of modifiable risk factors such as WC and sodium intake with methylation changes may shed light into novel pathogenic pathways for HTN.

Impaired gut motility may contribute, at least in part, to the development of systemic hyperammonemia and systemic neurological disorders in inherited metabolic disorders, or in severe liver and renal disease. It is not known whether enteric neurotransmission regulates intestinal luminal and hence systemic ammonia levels by induced changes in motility. Here, we propose and test the hypothesis that ammonia acts through specific enteric circuits to influence gut motility. We tested our hypothesis by recording the effects of ammonia on neuromuscular transmission in tissue samples from mice, pigs, and humans and investigated specific mechanisms using novel mutant mice, selective drugs, cellular imaging, and enzyme-linked immunosorbent assays. Exogenous ammonia increased neurogenic contractions and decreased neurogenic relaxations in segments of mouse, pig, and human intestine. Enteric glial cells responded to ammonia with intracellular Ca2+ responses. Inhibition of glutamine synthetase and the deletion of glial connexin-43 channels in hGFAP::CreERT2+/-/connexin43f/f mice potentiated the effects of ammonia on neuromuscular transmission. The effects of ammonia on neuromuscular transmission were blocked by GABAA receptor antagonists, and ammonia drove substantive GABA release as did the selective pharmacological activation of enteric glia in GFAP::hM3Dq transgenic mice. We propose a novel mechanism whereby local ammonia is operational through GABAergic glial signaling to influence enteric neuromuscular circuits that regulate intestinal motility. Therapeutic manipulation of these mechanisms may benefit a number of neurological, hepatic, and renal disorders manifesting hyperammonemia.NEW & NOTEWORTHY We propose that local circuits in the enteric nervous system sense and regulate intestinal ammonia. We show that ammonia modifies enteric neuromuscular transmission to increase motility in human, pig, and mouse intestine model systems. The mechanisms underlying the effects of ammonia on enteric neurotransmission include GABAergic pathways that are regulated by enteric glial cells. Our new data suggest that myenteric glial cells sense local ammonia and directly modify neurotransmission by releasing GABA.

BACKGROUND & AIMS: The concept of enteric glia as regulators of intestinal homeostasis is slowly gaining acceptance as a central concept in neurogastroenterology. Yet how glia contribute to intestinal disease is still poorly understood. Purines generated during inflammation drive enteric neuron death by activating neuronal P2X7 purine receptors (P2X7R); triggering adenosine triphosphate (ATP) release via neuronal pannexin-1 channels that subsequently recruits intracellular calcium ([Ca 2 1,) in surrounding enteric glia. We tested the hypothesis that the activation of enteric glia contributes to neuron death during inflammation.METHODS: We studied neuroinflammation in vivo using the 2,4-dinitrobenzene sulfonic acid model of colitis and in situ using whole-mount preparations of human and mouse intestine. Transgenic mice with a targeted deletion of glial connexin-43 (Cx43) [GFAP::Cre(ERT2+/-)/Cx43(f/f)] were used to specifically disrupt glial signaling pathways. Mice deficient in inducible nitric oxide (NO) synthase (iNOS(-/-)) were used to study NO production. Protein expression and oxidative stress were measured using immunohistochemistry and in situ Ca2+ and NO imaging were used to monitor glial [Ca2+](i) and [NO](i).RESULTS: Purinergic activation of enteric glia drove [Ca2+](i) responses and enteric neuron death through a Cx43-dependent mechanism. Neurotoxic Cx43 activity, driven by NO production from glial iNOS, was required for neuron death. Glial Cx43 opening liberated ATP and Cx43-dependent ATP release was potentiated by NO.CONCLUSIONS: Our results show that the activation of glial cells in the context of neuroinflammation kills enteric neurons. Mediators of inflammation that include ATP and NO activate neurotoxic pathways that converge on glial Cx43 hemichannels. The glial response to inflammatory mediators might contribute to the development of motility disorders.

Background: The development of common forms of hypertension (HTN) involves both genetic and environmental factors. Methylation changes (one of the epigenetic modifications) of DNA may play a role in the regulation of BP and development of HTN, and may result from interaction of specific genes with the environment. The current study investigates the relationship between genome-wide changes in DNA methylation in T-lymphocytes and BP level differences among monozygotic twins, who have identical DNA sequences. Methods: In a preliminary study, we recruited 24 pairs of monozygotic twins (60% women) with a mean age of 44 ± 10 years. Zygosity was determined via self-report or participants’ responses to a standard zygosity questionnaire. BPs were measured in triplicate after 5 minutes of rest at one minute intervals and averaged. Anthropometrics measurements were obtained along with blood for isolation of T-lymphocytes. DNA from T-lymphocytes was used to perform reduced representation bisulfite sequencing (RRBS) to measure methylation levels at single-base resolution in these subjects. Average differences in systolic (SBP) and diastolic (DBP) BPs were used as continuous variables for these analyses. Results: Mean SBP was 124 ± 15 (range (r): 97-174) mm Hg and mean DBP was 78 ± 11 (r: 49-106) mm Hg. Average differences in SBP and DBP among the co-twins (members of a twin pair) were 9 ± 10 (r: 0-40) mm Hg and 8 ± 6 (r: 0-26) mm Hg respectively. Average BMI was 29 ± 8 kg/m 2 . We observed that an average of 3063 (r: 757-7250) CpG islands were differentially methylated (DMRs) between co-twins. Among these DMRs, 10 were associated with average SBP difference and 5 were associated with average DBP difference at a significance level of p < 0.001. DMRs showing the strongest association (unadjusted p < 10 -4 ) between the co-twins were located in the transcriptional start site (TSS) of genes: CDC26 (cell division cycle protein) and NR2F6 (nuclear receptor) for average SBP difference and LEPRE1 (propyl 3 hydroxylase protein) for average DBP difference. Conclusions: BP differences between monozygotic co-twins, which most likely result from environmental factors, appear to be associated with differences in DNA methylation in T lymphocytes.

Hypertension (HT) and Type 2 diabetes (T2D) are more common in overweight and obese subjects, but mechanistic links have not been fully established. Some evidence indicates that low level inflammation, especially in visceral fat depots, provides one such link in part by promoting vascular remodeling/fibrosis. Here we sought to determine if inflammation and splanchnic vascular remodeling/fibrosis were more prevalent in obese women with hypertension and/or T2D than obese only.METHODSWe blindly evaluated H&E stained mesenteric vessels and perivascular adipose tissue obtained from 29 female patients who underwent Roux‐en‐Y bariatric surgery. Based on this evaluation, the patients were separated into two groups, according to the observed relatively prevalence and severity of histological alterations (vascular remodeling/fibrosis, angiogenesis, and inflammation). Tissues from 11 patients showed relatively mild histological changes (Group A), while tissues from the other 18 patients displayed more severe histological alterations (Group B). Based on their medical histories, the number of patients with HT, T2D, HT+T2D or neither condition (obese only: OO) were determined for both groups.RESULTSHT+T2D was slightly (but not significantly) higher in group B than group A (3/11, 27.7% vs 8/18, 44.4%). OO (3/11, 27.3% vs 5/18, 27.7%), HT (3/11, 27.3% vs 3/18, 16.6%), and T2D (3/11, 27.3% vs 2/18, 11.2%) were all similar in groups A and B. There were no differences in age (45 ± 3y vs 49 ± 2y), BMI (43.3 ± 3% vs 44.1 ± 2%) or occurrence of hyperlipidemia (6/11, 54.5% vs 9/18, 50%) between the two groups. To confirm our observations in H&E stained tissues, we randomly selected three patients from each category (OO, HT, T2D and HT+T2D), and evaluated vascular remodeling/fibrosis in Masson's trichrome stained tissues (for collagen) and macrophage infiltration into perivascular adipose tissue (CD 68 staining). The results showed no correlation between vascular remodeling/fibrosis, or adipose tissue inflammation, and HT or T2D.CONCLUSIONSOur studies do not support the hypothesis that inflammation and vascular remodeling/fibrosis in the splanchnic region cause hypertension or T2D in obese women.Support or Funding InformationSupported by NIH 2P01HL070687 (For Drs Fink, Galligan, Watts and Xu)

Obesity and hypertension have become comorbid in near epidemic proportion, yet their biological connection is still largely a mystery. We hypothesized that the peptide chemerin (TIG2) is a candidate for connecting fat deposits (both perivascular and visceral) to elevated blood pressure. The normal Sprague Dawley or deoxycorticosterone acetate salt (DOCA) rat was used as the model. Real time RT-PCR demonstrated that chemerin was synthesized in periadventitial fat (PVAT) around the aorta. Immunohistochemical experiments showed that the primary receptor for chemerin, ChemR23, was expressed in the tunica media and endothelial layer and not in resident inflammatory cells of the artery. The potent analog chemerin-9 (1 nM — 3 uM) caused a concentration-dependent isometric contraction in isolated aorta and superior mesenteric artery that was modest in tissues at baseline [∼6-11% phenylephrine (PE) maximum contraction] but significantly amplified in the presence of the nitric oxide synthase inhibitor nitro-L-arginine (LNNA; 2.5 fold increase in maximum), endothelial removal (5.95 fold increase) or agonist-induced tone (3.2 fold increase). Chemerin-induced contraction in tissues incubated with LNNA was concentration-dependently antagonized by the novel ChemR23 antagonist CCX832, demonstrating a new role for ChemR23. Arteries from the DOCA-salt hypertensive rat demonstrated endothelial dysfunction, and chemerin-induced maximum contraction from baseline was markedly increased in the aorta (DOCA = 16+3.6%, Sham = 6.7 + 2.2% PE contraction) and superior mesenteric artery (DOCA=57.9+12.8, Sham = 11.2+2.9 % PE contraction; p<0.05). These data support a new role for chemerin as a vasoactive substance and a potential connector of the biological activity of the adipose tissue and liver (sources of chemerin) to blood pressure regulation, especially in conditions of endothelial dysfunction.

Small mesenteric veins (MV) are important in regulation of blood pressure via their capacitance function, however, our previous studies showed that MV displayed heterogeneity in pharmacological responses across species. For example, the large conductance Ca2+ activated K+ (BK) channels and L‐type Ca2+ channels control basal tone and spontaneous oscillations in tone in rat but not murine MV. It is unknown if BK and L‐type Ca2+ channels function in human MV. Therefore, we tested BK and L‐type Ca2+ channel function in isolated and pressurized MA (mesenteric arteries) (60 mmHg) and MV (4 mmHg) from small segments of jejunum harvested from specimens obtained from obese subjects undergoing gastric bypass surgery. The patients reported here were female, 23–45 years old, with BMI values between 34–54, but without hypertension or diabetes. We measured drug‐induced changes in outside diameter and found that: 1) Norepinephrine (NE) dose‐response curves were similar in MA (n=4) and MV (n=4). 2) Nifedipine completely blocked Bay K 8644 (L‐type Ca2+ channel agonist)‐induced MA and MV constriction. 3) Nifedipine also blocked KCl (20–60 mM)‐induced MA, and KCl (20–40 mM)‐induced MV constriction. 4) At physiological intraluminal pressure, MV, but not MA, displayed basal tone and oscillating constrictions which were blocked by nifedipine or removing extracellular Ca2+. 5) Paxilline, a BK channel blocker, caused a 20% constriction in MA. 6) Paxilline did not constrict MV, but completely inhibited spontaneous oscillations in tone. Our results indicate that both BK and L‐type Ca2+ channels regulate human MA and MV tone, but act via blood vessel specific mechanisms. Pharmacological responses of human MV are similar to those of the rat but not the mouse.

whether TRPC3 up-regulation in aorta from SHR is associated with angiotensin II receptor (AT1R) mediate calcium influx. Methods: Blood pressure was measured using tail-cuff plethys-mography and a pressure transducer. Vasoconstriction of aortic rings was measured by organ chamber. Aortic smooth muscle cells (VSMCs) was cultured. Cytosolic calcium concentration was measured by the fluorescence technique. TRPC3 and AT1R expressions were detected by western blotting. Results TRPC3 expression was significantly increased in aorta form SHR compared to WKY (1.48 0.05 vs. 1.00 0.06, p 0.01). AT1R expression was no significantly difference in aorta from SHR compared to WKY (p 0.05). Administration of Ang II significantly increased TRPC3 expression in VSMCs from SHR compared to SHR control conditions (p 0.05). Administration of telmisartan, an AT1R blocker, significantly down regulated TRPC3 expression in cultured VSMCs (p 0.05). Immuno-fluorescence showed that TRPC3 and AT1R coexisted in cultured VSMC. Ang II significantly increased mean arterial blood pressure in SHR compared to WKY (53 3 vs. 22 4 mmHg, p 0.01). AngII-induced vasoconstriction was significantly higher in aortic rings from SHR compared to WKY (82 3% vs. 54 6%, p 0.01). After administration of telmisartan (5mg/kg/day) in SHR for 4 weeks systolic blood pressure was significantly reduced from 202 20 mmHg to 124 18 mmHg (n 6, p 0.01). Upregulation of TRPC3 by overexpressing TRPC3 gene in the cultured VSMCs significantly increased TRPC3 expression (p 0.01), and AngII-induced calcium influx was significantly increased to 155 12% (n 6; p 0.01). After siRNA against TRPC3 significantly reduced TRPC3 expression by 30 5% in the cultured VSMCs and Ang II-induced calcium influx was accompanied reduced (p 0.05). Conclusion This study for the first time highlights the importance of AT1R mediated the calcium influx through TRPC3 channel in genetic hypertension (supported by 973 program 2006CB503804).

Many cellular genes involved in immunity and inflammation are regulated at the level of transcription by nuclear factor kappa B (NFkB). Products of these genes include TNF‐alpha and interleukin‐6 (IL‐6). Increased plasma levels of these inflammatory cytokines (IL‐6, TNF‐alpha, etc.) are seen in hypertension (HTN), suggesting that vascular inflammation is part of the pathophysiology of HTN. To our knowledge no one has previously measured NFkB in blood vessels of hypertensive patients. Study objective: Measure NFkB tissue levels in internal mammary artery (IMA) and saphenous vein (SV) tissue in hypertensive and normotensive patients undergoing coronary artery bypass graft (CABG) surgery.MethodsA TransAM NFkB p50 colorimetric ELISA kit was used to measure NFkB content in the vessels in 79 patients undergoing CABG surgery. The patients were interviewed and their hospital charts were abstracted to determine whether the patients had HTN and/or type 2 diabetes.ResultsWe found that there was no significant difference in NFkB p50 activity levels in human IMA or SV between hypertensive and normotensive patients undergoing CABG surgery. We also found that the presence of type 2 diabetes did not affect these levels.ConclusionThese data suggest that vascular inflammation in HTN does not require increased vascular production of NFkB. Grant Support: NIH HL73251.

Hypertension (HTN) and cardiovascular disease are the most common causes of death in developed countries. The use of experimental animal models of HTN has provided valuable information regarding many aspects of HTN, including etiology, pathophysiology, complications, and treatment. Because the etiology of HTN is heterogeneous, many experimental animal models have been developed to mimic the many facets of human HTN. The choice of animal model will be determined by the research question, monetary limitations, and technical expertise. The categories of models of HTN are: renovascular, renal parenchymal, pharmacologically induced, environmentally induced, and genetic. There are considerable differences between HTN in animals and humans, including differences in homeostatic mechanisms and pathophysiology; therefore, a thorough understanding of the animal models and rigorous analysis is required before extrapolating the finding in animals to humans.

Asian/Pacific Islander Americans (APIAs) are the fastest growing population in the United States by percentage. Hypertension is common and increases cardiovascular risk to a great extent in this population. The medical problems of this group are being increasingly encountered by US physicians. Many gene mutations associated with hypertension are more common in Asians. The significance of these polymorphisms in the pathogenesis of hypertension in APIAs is unclear. The percentage of APIAs who are aware, treated, and controlled is small. There may be some differences in the responses to antihypertensive medications between APIAs and whites. The results of human studies on the effect of drinking of tea on blood pressure in different groups are conflicting. Cough associated with angiotensin-converting enzyme inhibitor therapy may be more common in APIAs than in whites. There is a need for more education of APIAs regarding hypertension and for more effective treatment of hypertension by the physicians caring for this population.

Remodeling of arteries occurs in hypertension (HTN). Intraluminal pressure stimulates growth. Venous pressure is not increased in systemic (HTN), and evidence for remodeling of small veins is less clear. This study is the first to compare the structure of small resistance arteries and small veins in the Dahl salt‐sensitive (SS) rat model of HTN. Both the SS and salt‐resistant (SR) rats were fed regular rat chow for 8 weeks. The average systolic blood pressure for the SS 182 + 2 mm Hg, for the SR 137 + 2 mm Hg. We studied 10 SS and 9 SR mesenteric veins and 9 SS and 9 SR mesenteric arteries. The arteries and veins were mounted on glass microcannulae in calcium free Kreb's solution and measurements were made using a pressure myograph. Results: In the arteries, the SS had higher wall thickness (WT) (p=0.003), media/lumen ratio (M/L) (p=0.006), and cross‐sectional area (CSA) (p=0.005). There was no difference in lumen diameter (LD) or incremental distensibility (ID). There were no differences betweent the SS and SR veins in WT, M/L, CSA, LD, or ID. Conclusions: In Dahl rat HTN, we found that arteries of the hypertensive (SS) rats showed remodeling, while the veins had no remodeling. Although pressure is not increased in the veins in HTN the neurohumoral milieu is similar to that in arteries. This suggests that intraluminal pressure is the major cause of the remodeling seen in hypertensive arterial walls.

Smooth muscle myosin heavy chains occur in 2 isoforms, SMA (slow) and SMB (fast). We hypothesized that the SMB isoform is predominant in the faster-contracting rat vena cava compared to thoracic aorta. We compared the time to half maximal contraction in response to a maximal concentration of endothelin-1 (ET-1; 100 nM), potassium chloride (KCl; 100 mM) and norepinephrine (NE; 10 µM). The time to half maximal contraction was shorter in the vena cava compared to aorta (aorta: ET-1 = 235.8 ± 13.8 s, KCl = 140.0 ± 33.3 s, NE = 19.8 ± 2.7 s; vena cava: ET-1 = 121.8 ± 15.6 s, KCl = 49.5 ± 6.7 s, NE = 9.0 ± 3.3 s). Reverse-transcription polymerase chain reaction supported the greater expression of SMB in the vena cava compared to aorta. SMB was expressed to a greater extent than SMA in the vessel wall of the vena cava. Western analysis determined that expression of SMB, relative to total smooth muscle myosin heavy chains, was 12.5 ± 4.9-fold higher in the vena cava compared to aorta, while SMA was 4.9 ± 1.2-fold higher in the aorta than vena cava. Thus, the SMB isoform is the predominant form expressed in rat veins, providing one possible mechanism for the faster response of veins to vasoconstrictors.

Arterial remodeling occurs in response to mechanical and neurohumoral stimuli. We hypothesized that veins, which are not exposed to higher pressures in hypertension, would demonstrate less active remodeling than arteries. We assessed remodeling with two standard measures of arterial remodeling: vessel morphometry and the expression/function of matrix metalloproteinases (MMPs). Thoracic aorta and vena cava from sham normotensive and DOCA-salt hypertensive rats (110 +/- 4 and 188 +/- 8 mmHg systolic blood pressure, respectively) were used. Wall thickness was increased in DOCA-salt vs. sham aorta (301 +/- 23 vs. 218 +/- 14 mum, P < 0.05), as was medial area, but neither measure was altered in the vena cava. The aorta and vena cava expressed the gelatinases MMP-2, MMP-9, transmembrane proteinase MT1-MMP, and tissue inhibitor of metalloproteinase-2 (TIMP-2). Immunohistochemically, MMP-2 localized to smooth muscle in the aorta and densely in endothelium/smooth muscle of the vena cava. Western and zymographic analyses verified that MMP-2 was active in all vessels and less active in the vena cava than aorta. In hypertension, MMP-2 expression and activity in the aorta were increased (59.1 +/- 3.7 and 74.5 +/- 6.1 units in sham and DOCA, respectively, P < 0.05); similar elevations were not observed in the vena cava. MMP-9 was weakly expressed in all vessels. MT1-MMP was expressed by the aorta and vena cava and elevated in the vena cava from DOCA-salt rats. TIMP-2 expression was significantly increased in the aorta of DOCA rats compared with sham but was barely detectable in the vena cava of sham or DOCA-salt hypertensive rats. These findings suggest that large veins may not undergo vascular remodeling in DOCA-salt hypertension.