Asymmetric dimethylarginine (ADMA), which inhibits NO synthase, is inactivated by N G , N G -dimethylarginine dimethylaminohydrolase (DDAH). We tested whether DDAH-1 or -2 regulates serum ADMA (S ADMA ) and/or endothelium-derived relaxing factor (EDRF)/NO. Small inhibitory (si)RNAs targeting DDAH-1 or -2, or an siRNA control were given intravenously to rats. After 72 hours, EDRF/NO was assessed from acetylcholine-induced, NO synthase–dependent relaxation and 4-amino-5-methylamino-2′,7′-diflouroflourescein diacetate for NO activity in isolated mesenteric resistance vessels (MRVs). Expression of mRNA for DDAH-1 versus -2 was 2- and 7-fold higher in the kidney cortex and liver, respectively, whereas expression of DDAH-2 versus -1 was 5-fold higher in MRVs. The proteins and mRNAs for DDAH-1 or -2 were reduced selectively by 35% to 85% in the kidney cortex, liver, and MRVs 72 hours following the corresponding siRNA. S ADMA was increased only after siDDAH-1 (266±25 versus 342±39 [mean±SD] nmol · L −1 ; P <0.005), whereas EDRF/NO responses and NO activity were not changed consistently by siDDAH-1 but were greatly reduced after siDDAH-2. Mean arterial pressure was not changed significantly by any siRNA. In conclusion, S ADMA is regulated by DDAH-1, which is expressed at sites of ADMA metabolism in the kidney cortex and liver, whereas EDRF/NO is regulated primarily by DDAH-2, which is expressed strongly in blood vessels. This implies specific functions of DDAH isoforms.

Nouri P, Gill P, Li M, Wilcox CS, Welch WJ. p22 in the macula densa regulates single nephron GFR during angiotensin II infusion in rats. Am J Physiol Heart Circ Physiol 292: H1685–H1689, 2007. First published January 12, 2007; doi:10.1152/ajpheart.00976.2006.—Angiotensin II (ANG II) infusion increases renal superoxide (O2 ) and enhances renal vasoconstriction via macula densa (MD) regulation of tubuloglomerular feedback, but the mechanism is unclear. We targeted the p22 subunit of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) with small-interfering RNA (siRNA) to reduce NADPH oxidase activity and blood pressure response to ANG II in rats. We compared single nephron glomerular filtration rate (SNGFR) in samples collected from the proximal tubule (PT), which interrupts delivery to the MD, and from the distal tubule (DT), which maintains delivery to the MD, to assess MD regulation of GFR. SNGFR was measured in control and ANG II-infused rats (200 ng kg 1 min 1 for 7 days) 2 days after intravenous injection of vehicle or siRNA directed to p22 to test the hypothesis that p22 mediates MD regulation of SNGFR during ANG II. The regulation of SNGFR by MD, determined by PT SNGFR-DT SNGFR, was not altered by siRNA in control rats (control vehicle, 13 1, n 8; control siRNA, 12 2 nl/min, n 8; not significant) but was reduced by siRNA in ANG II-treated rats (ANG II vehicle, 13 2, n 7; ANG II siRNA, 7 1 nl/min, n 8; P 0.05). We conclude that p22 and NADPH oxidase regulate the SNGFR during ANG II infusion via MD-dependent mechanisms.

Welch WJ, Patel K, Modlinger P, Mendonca M, Kawada N, Dennehy K, Aslam S, Wilcox CS. Roles of vasoconstrictor prostaglandins, COX-1 and -2, and AT1, AT2, and TP receptors in a rat model of early 2K,1C hypertension. Am J Physiol Heart Circ Physiol 293: H2644–H2649, 2007. First published August 31, 2007; doi:10.1152/ajpheart.00748.2007.—Angiotensin (ANG) II activating type 1 receptors (AT1Rs) enhances superoxide anion (O2 ) and arachidonate (AA) formation. AA is metabolized by cyclooxygenases (COXs) to PGH2, which is metabolized by thromboxane (Tx)A2 synthase to TxA2 or oxidized to 8-isoprostane PGF2 (8-Iso) by O2 . PGH2, TxA2, and 8-Iso activate thromboxane-prostanoid receptors (TPRs). We investigated whether blood pressure in a rat model of early (3 wk) two-kidney, one-clip (2K,1C) Goldblatt hypertension is maintained by AT1Rs or AT2Rs, driving COX-1 or -2-dependent products that activate TPRs. Compared with sham-operated rats, 2K,1C Goldblatt rats had increased mean arterial pressure (MAP; 120 4 vs. 155 3 mmHg; P 0.001), plasma renin activity (PRA; 22 7 vs. 48 5 ng ml 1 h ; P 0.01), plasma malondialdehyde (1.07 0.05 vs. 1.58 0.16 nmol/l; P 0.01), and TxB2 excretion (26 4 vs. 51 7 ng/24 h; P 0.01). Acute graded intravenous doses of benazeprilat (angiotensin-converting enzyme inhibitor) reduced MAP at 20 min ( 36 5 mmHg; P 0.001) and excretion of TxA2 metabolites. Indomethacin (nonselective COX antagonist) or SC-560 (COX-1 antagonist) reduced MAP at 20 min ( 25 5 and 28 7 mmHg; P 0.001), whereas valdecoxib (COX-2 antagonist) was ineffective ( 9 5 mmHg; not significant). Losartan (AT1R antagonist) or SQ-29548 (TPR antagonist) reduced MAP at 150 min ( 24 6 and 22 3 mmHg; P 0.001), whereas PD-123319 (AT2R antagonist) was ineffective. Acute blockade of TPRs, COX-1, or COX-2 did not change PRA, but TxB2 generation by the clipped kidney was reduced by blockade of COX-1 and increased by blockade of COX-2. 2K,1C hypertension in rats activates renin, O2 , and vasoconstrictor PGs. Hypertension is maintained by AT1Rs and by COX-1, but not COX-2, products that activate TPRs.

Angiotensin (ANG) II activating type 1 receptors (AT(1)Rs) enhances superoxide anion (O(2)*(-)) and arachidonate (AA) formation. AA is metabolized by cyclooxygenases (COXs) to PGH(2), which is metabolized by thromboxane (Tx)A(2) synthase to TxA(2) or oxidized to 8-isoprostane PGF(2alpha) (8-Iso) by O(2)*(-). PGH(2), TxA(2), and 8-Iso activate thromboxane-prostanoid receptors (TPRs). We investigated whether blood pressure in a rat model of early (3 wk) two-kidney, one-clip (2K,1C) Goldblatt hypertension is maintained by AT(1)Rs or AT(2)Rs, driving COX-1 or -2-dependent products that activate TPRs. Compared with sham-operated rats, 2K,1C Goldblatt rats had increased mean arterial pressure (MAP; 120 +/- 4 vs. 155 +/- 3 mmHg; P < 0.001), plasma renin activity (PRA; 22 +/- 7 vs. 48 +/- 5 ng x ml(-1) x h(-1); P < 0.01), plasma malondialdehyde (1.07 +/- 0.05 vs. 1.58 +/- 0.16 nmol/l; P < 0.01), and TxB(2) excretion (26 +/- 4 vs. 51 +/- 7 ng/24 h; P < 0.01). Acute graded intravenous doses of benazeprilat (angiotensin-converting enzyme inhibitor) reduced MAP at 20 min (-36 +/- 5 mmHg; P < 0.001) and excretion of TxA(2) metabolites. Indomethacin (nonselective COX antagonist) or SC-560 (COX-1 antagonist) reduced MAP at 20 min (-25 +/- 5 and -28 +/- 7 mmHg; P < 0.001), whereas valdecoxib (COX-2 antagonist) was ineffective (-9 +/- 5 mmHg; not significant). Losartan (AT(1)R antagonist) or SQ-29548 (TPR antagonist) reduced MAP at 150 min (-24 +/- 6 and -22 +/- 3 mmHg; P < 0.001), whereas PD-123319 (AT(2)R antagonist) was ineffective. Acute blockade of TPRs, COX-1, or COX-2 did not change PRA, but TxB(2) generation by the clipped kidney was reduced by blockade of COX-1 and increased by blockade of COX-2. 2K,1C hypertension in rats activates renin, O(2)*(-), and vasoconstrictor PGs. Hypertension is maintained by AT(1)Rs and by COX-1, but not COX-2, products that activate TPRs.

The angiotensin II (Ang II) slow-pressor response entails an increase in mean arterial pressure and reactive oxygen species. We used double-stranded interfering RNAs (siRNAs) in Sprague Dawley rats in vivo to test the hypothesis that an increase in the p22phox component of NADPH oxidase is required for this response. Reactive oxygen species were assessed from excretion of 8-isoprostane prostaglandin F2alpha and blood pressure by telemetry. Two siRNA sequences to p22phox (sip22phox) reduced mRNA >85% in cultured vascular smooth muscle cells. Rats received rapid (10 second) IV injections (50 to 100 microg) of 1 of 2 different sip22phox, control siRNA, or vehicle (TransIt in saline) during 14 day SC infusions of Ang II (200 ng.kg(-1).min(-1)) or sham infusions. In both groups, sip22phox, relative to control siRNA, led to significant (P<0.001; approximately 50%) reductions in expression of p22phox mRNA and protein and of NADPH oxidase activity in the kidney cortex. In Ang II-infused rats, sip22phox decreased protein expression for Nox-1, -2, and -4 but increased p47phox. Three days after sip22phox, conscious rats infused with Ang II had a reduced excretion of 8-isoprostane (10+/-1 versus 19+/-2 pg.24 h(-1); P<0.01) and a reduced mean arterial pressure (142+/-5 versus 168+/-4 mm Hg; P<0.005). An increase in p22phox is required for increased renal NADPH oxidase activity, expression of Nox proteins and oxidative stress, and contributes < or =50% to hypertension during an Ang II slow-pressor response.

We used cyclooxygenase-1 (COX-1)-deficient mice to test the hypothesis that COX-1 regulates blood pressure (BP) and renal hemodynamics. The awake time (AT) mean arterial pressures (MAPs) measured by telemetry were not different between COX-1(+/+) and COX-1(-/-) (131+/-2 versus 126+/-3 mm Hg; NS). However, COX-1(-/-) had higher sleep time (ST) MAP (93+/-1 versus 97+/-2 mm Hg; P<0.05) and sleep-to-awake BP ratio (+8.6%; P<0.05). Under anesthesia with moderate sodium loading, COX-1(-/-) had higher MAP (109+/-5 versus 124+/-4 mm Hg; P<0.05), renal vascular resistance (23.5+/-1.6 versus 30.7+/-1.7 mm Hg . mL(-1) . min(-1) . g(-1); P<0.05) and filtration fraction (33.7+/-2.1 versus 40.2+/-2.0%; P<0.05). COX-1(-/-) had a 89% reduction (P<0.0001) in the excretion of TxB2, a 76% reduction (P<0.01) in PGE2, a 40% reduction (P<0.0002) in 6-ketoPGF1alpha (6keto), a 27% reduction (P<0.02) in 11-betaPGF2alpha (11beta), a 35% reduction (P<0.01) in nitrate plus nitrite (NOx), and a 52% increase in metanephrine (P<0.02). The excretion of normetanephrine, a marker for sympathetic nervous activity, was reduced during ST in COX-1(+/+) (6.9+/-0.9 versus 3.2+/-0.6 g . g(-1) creatinine . 10(-3); P<0.01). This was blunted in COX-1(-/-) (5.1+/-0.9 versus 4.9+/-0.7 g . g(-1) creatinine . 10(-3); NS). Urine collection during ST showed lower excretion of 6keto, 11beta, NOx, aldosterone, sodium, and potassium than during AT in both COX-1(+/+) and COX-1(-/-), and there were positive correlations among these parameters (6keto versus NOx; P<0.005; 11beta versus NOx; P<0.005; and NOx versus sodium; P<0.005). In conclusion, COX-1 mediates a suppressed sympathetic nervous activity and enhanced NO, which may contribute to renal vasodilatation and a reduced MAP while asleep or under anesthesia. COX-1 contributes to the normal nocturnal BP dipping phenomenon.

We investigated the hypothesis that thromboxane A2 (TxA2)-prostaglandin H2 receptors (TP-Rs) mediate the hemodynamic responses and increase in reactive oxygen species (ROS) to ANG II (400 ng x kg(-1) x min(-1) sc for 14 days) using TP-R knockout (TP -/-) and wild-type (+/+) mice. TP -/- had normal basal mean arterial blood pressure (MAP) and glomerular filtration rate but reduced renal blood flow and increased filtration fraction (FF) and renal vascular resistance (RVR) and markers of ROS (thiobarbituric acid-reactive substances and 8-isoprostane PGF2alpha) and nitric oxide (NOx). Infusion of ANG II into TP +/+ increased ROS and thromboxane B2 (TxB2) and increased RVR and FF. ANG II infusion into TP -/- mice reduced ANG I and increased aldosterone but caused a blunted increase in MAP (TP -/- : +6 +/- 2 vs. TP +/+: +15 +/- 3 mmHg) and failed to increase FF, ROS, or TxB2 but increased NOx and paradoxically decreased RVR (-2.1 +/- 1.7 vs. +2.6 +/- 0.8 mmHg x ml(-1) x min(-1) x g(-1)). Blockade of AT1 receptor of TP -/- mice infused with ANG II reduced MAP (-8 mmHg) and aldosterone but did not change the RVR or ROS. In conclusion, during an ANG II slow pressor response, AT1 receptors activate TP-Rs that generate ROS and prostaglandins but inhibit NO. TP-Rs mediate all of the increase in RVR and FF, part of the increase in MAP, but are not implicated in the suppression of ANG I or increase in aldosterone. TP -/- mice have a basal increase in RVR and FF associated with ROS.

Purpose of reviewThis review will examine the most recent evidence that adenosine receptors in the kidney can alter kidney function. Adenosine A1-receptors located in the afferent arteriole and proximal tubule can contribute to fluid retaining disorders by mediating tubuloglomerular feedback, afferent arteriole vasoconstriction or direct sodium absorption. In addition, A1-receptors may have a role for the prevention or treatment of ischemic injury to the kidney by maintaining afferent arteriole vasodilatation and preserving the glomerular filtration rate. Recent findingsAnimal and human studies confirm that adenosine A1-receptor antagonists are useful adjuvants to the treatment of congestive heart failure by increasing diuresis and natriuresis and preserving the glomerular filtration rate. These agents most likely function to directly inhibit tubular absorption of sodium, as well as inhibit tubuloglomerular feedback. There is increasing evidence that adenosine A1-receptors directly affect the release of renin, and that adenosine and angiotensin II act synergistically to increase renal vascular resistance and decrease renal blood flow. The ability of adenosine A1-receptor antagonists to preserve the glomerular filtration rate and protect the kidney against ischemic damage or drug toxicity is not well established. SummaryThe utility of adenosine A1-receptor antagonists in the treatment of congestive heart failure should lead to larger clinical trials of these agents. There is increasing evidence that the receptors mediate vasoconstriction that is unique to the renal microcirculation. However, studies of adenosine A1-receptor antagonists in animal models have largely been unsuccessful in preventing ischemic kidney damage, most likely due to the diversity of factors and events that are involved.

OBJECTIVES:Recent surveys of physician practice have suggested the existence of excessive, inappropriate use of the fecal occult blood test (FOBT). We studied the implementation of this test in hospitalized patients. METHODS:We performed a retrospective chart review of 1000 randomly selected patients who had been discharged from the Medicine service at four teaching hospitals. Patient demographics, clinical presentation, presence or absence of overt GI bleeding, and use of medications that might affect the FOBT were recorded. Reviewers assessed whether patients who had FOBT would have been candidates for colon resection if asymptomatic colon cancer had been found. RESULTS:Digital rectal examination was documented in 44.8% of patients; the findings were recorded in only 9%. A total of 421 patients had FOBT on admission, usually on stool obtained at digital rectal examination. Of the patients with a positive FOBT, 17% had active GI bleeding. Only 41.1% of patients with a positive FOBT were referred to the gastroenterology service. In 70.5% of patients, FOBT could be considered inappropriate because of factors such as age, active GI bleeding, or use of aspirin or other nonsteroidal anti-inflammatory drugs. CONCLUSIONS:The FOBT, which is validated only for colorectal cancer screening, is often performed inappropriately in patients admitted to the hospital. This test should be restricted in hospital practice. It would be preferable to identify patients who are appropriate candidates for colorectal cancer screening at the time of hospital discharge and to advise them about the appropriate performance of the FOBT at home.

Aim: To compare the value of endoscopic ultrasound (EUS), magnetic resonance imaging (MRI), ERCP, CT and transabdominal ultrasound (US) in the evaluation of ampullary (AT) and pancreatic tumors (PT).Patients and methods: 85 patients (52 men, mean age 68 y, range 32-88 years) with clinical suspicion of AT or PT underwent EUS (n=85), MRI with MRCP (n=65), ERCP (n=85), CT (n =74) and US (n =84).The final diagnosis of a malignant (n=44), benign (n= 13) or no tumor (n=24) was made at surgerylbiopsy (n=51) or a 6-17 month follow up (n=30).No final diagnosis could be reached in 4 patients, who were not included in the evaluation.Of the 44 malignant tumors (14 AT and 30 PT)43 were adeno-carcinomas and I was a carcinoid.10 of 13 benign tumors were located in the ampullary region.Results: see table There is a significant difference between EUS-MRI (p=0.003),EUS-CT (p= 0,006) and EUS-US (p= 0.0001).Especially with respect to the 25 tumors of 2cm or less (20 AT and 5 PT).EUS could detect all small tumors (25/25), MRI (10120), ERCP (19/25), CT (9/19) and US (8/25).The smallest tumor visualized by EUS was 1.0 em in diameter.Conclusion:EUS is more accurate than MRI.ERCP, CT and US in the diagnosis of AT and PT.EUS is the method of choise in visualizing small tumors of 2 em or less, which have a chance of curative treatment.EUS can not reliably distinguish between neoplastic and inflammatory tumors.Results: Performance ofthe five imaging technics intumor visualisation: Sens. (%) Spec (%) PPV(%) NPV(%) Accuracy (%) EUS 81