Background— Inhibition of tyrosine kinases, including platelet-derived growth factor receptor, can reduce pulmonary arterial pressure in experimental and clinical pulmonary hypertension. We hypothesized that inhibition of the serine/threonine kinases Raf-1 (also termed c-Raf) and b-Raf in addition to inhibition of tyrosine kinases effectively controls pulmonary vascular and right heart remodeling in pulmonary hypertension. Methods and Results— We investigated the effects of the novel multikinase inhibitor sorafenib, which inhibits tyrosine kinases as well as serine/threonine kinases, in comparison to imatinib, a tyrosine kinase inhibitor, on hemodynamics, pulmonary and right ventricular (RV) remodeling, and downstream signaling in experimental pulmonary hypertension. Fourteen days after monocrotaline injection, male rats were treated orally for another 14 days with sorafenib (10 mg/kg per day), imatinib (50 mg/kg per day), or vehicle (n=12 to 16 per group). RV systolic pressure was decreased to 35.0±1.5 mm Hg by sorafenib and to 54.0±4.4 mm Hg by imatinib compared with placebo (82.9±6.0 mm Hg). In parallel, both sorafenib and imatinib reduced RV hypertrophy and pulmonary arterial muscularization. The effects of sorafenib on RV systolic pressure and RV mass were significantly greater than those of imatinib. Sorafenib prevented phosphorylation of Raf-1 and suppressed activation of the downstream ERK1/2 signaling pathway in RV myocardium and the lungs. In addition, sorafenib but not imatinib antagonized vasopressin-induced hypertrophy of the cardiomyoblast cell line H9c2. Conclusions— The multikinase inhibitor sorafenib prevents pulmonary remodeling and improves cardiac and pulmonary function in experimental pulmonary hypertension. Sorafenib exerts direct myocardial antihypertrophic effects, which appear to be mediated via inhibition of the Raf kinase pathway. The combined inhibition of tyrosine and serine/threonine kinases may provide an option to treat pulmonary arterial hypertension and associated right heart remodeling.

The chromanol 293B (293B, trans-6-cyano-4-(N-ethylsulfonyl-N-methylamino)-3-hydroxy-2,2-dimethyl-chroman) is a lead compound of potential class III antiarrhythmics that inhibit cardiac I(Ks) potassium channels. These channels are formed by the coassembly of KCNQ1 (Kv7.1, KvLQT1) and KCNE1 subunits. Although homomeric KCNQ1 channels are the principal molecular targets, entry of KCNE1 to the channel complex enhances the chromanol block. Because closely related neuronal KCNQ2 potassium channels are insensitive to the drug, we used KCNQ1/KCNQ2 chimeras to identify the binding site of the inhibitor. We localized the putative drug receptor to the H5 selectivity filter and the S6 transmembrane segment. Single residues affecting 293B inhibition were subsequently identified through systematic exchange of amino acids that were either different in KCNQ1 and KCNQ2 or predicted by a docking model of 293B in the open and closed conformation of KCNQ1. Mutant channel proteins T312S, I337V, and F340Y displayed dramatically lowered sensitivity to chromanol block. The predicted drug binding receptor lies in the inner pore vestibule containing the lower part of the selectivity filter, and the S6 transmembrane domain also reported to be important for binding of benzodiazepines. We propose that the block of the ion permeation pathway involves hydrophobic interactions with the S6 transmembrane residues Ile337 and Phe340, and stabilization of chromanol 293B binding through electrostatic interactions of its oxygen atoms with the most internal potassium ion within the selectivity filter.

The heme-enzyme soluble guanylyl cyclase (sGC) is an ubiquitous NO receptor, which mediates NO downstream signaling by the generation of cGMP. We studied the mechanism of action of the anthranilic acid derivatives 5-chloro-2-(5-chloro-thiophene-2-sulfonylamino-N-(4-(morpholine-4-sulfonyl)-phenyl)-benzamide sodium salt (HMR1766) (proposed international nonproprietary name, ataciguat sodium) and 2-(4-chloro-phenylsulfonylamino)-4,5-dimethoxy-N-(4-(thiomorpholine-4-sulfonyl)-phenyl)-benzamide (S3448) as a new class of sGC agonists. Both compounds activated different sGC preparations (purified from bovine lung, or crude from human corpus cavernosum) in a concentration-dependent and quickly reversible fashion (EC50 = 0.5-10 microM), with mixed-type activation kinetics. Activation of sGC by these compounds was additive to activation by NO donors, but instead of being inhibited, it was potentiated by the heme-iron oxidants 1H-[1,2,4]-oxdiazolo[3,4-a]quinoxalin-1-one (ODQ) and 4H-8-bromo-1,2,4-oxadiazolo(3,4-d) benz(b)(1,4)oxazin-1-one (NS2028), suggesting that the new compounds target the ferric heme sGC isoform. Protoporphyrin IX acted as a competitive activator, and zinc-protoporphyrin IX inhibited activation of heme-oxidized sGC by HMR1766 and S3448, whereas heme depletion of sGC by Tween 20 treatment reduced activation. Both compounds increased cGMP levels in cultured rat aortic smooth muscle cells; induced vasorelaxation of isolated endothelium-denuded rat aorta, porcine coronary arteries, and human corpus cavernosum (EC50 1 to 10 microM); and elicited phosphorylation of the cGMP kinase substrate vasodilator-stimulated phosphoprotein at Ser239. HMR1766 intravenous bolus injection decreased arterial blood pressure in anesthetized pigs. All of these pharmacological responses to the new compounds were enhanced by ODQ and NS2028. Our findings suggest that HMR1766 and S3448 preferentially activate the NO-insensitive heme-oxidized form of sGC, which exists to a variable extent in vascular tissues, and is a pharmacological target for these new vasodilator drugs.

Vasoconstrictor factors, like urotensin, angiotensin and catecholamines, activate Rho-dependent serine–threonine kinase (Rho-kinase) and inhibition of this pathway represents a novel therapy for cardiovascular diseases with hypertensive syndrome. The disbalance of relaxing endothelial nitric oxide (NO)-producing and vasoconstrictive pathways can be especially important in diseases where hypertension is accompanied by endothelial dysfunction that compromises NO generation. However, a recent study reported that the efficacy of the Rho-kinase inhibitor (R)-(+)-trans-N-(4-Pyridyl)-4-(1-aminoethyl)cyclohexanecarboxamide (Y27632) is dramatically attenuated upon removal of endothelium or inhibition of endothelial NO synthase (eNOS). This raises the question whether Rho-kinase inhibition could be an effective treatment in case of hypertension associated with endothelial dysfunction. The purpose of the present study was to determine whether the vasorelaxing effect of Rho-kinase inhibition is mediated through eNOS-dependent mechanisms. We show here that in the models of genetically reduced endothelial NO production (eNOS−/− mice and spontaneous hypertensive rats (SHR)) or in models of pharmacologically reduced endogenous NO production (N(omega)-nitro-l-arginine methyl ester (LNAME) treatment), Rho-kinase inhibition induced a strong vasodilation and reduction of blood pressure indicating independence of Rho-kinase pathway from eNOS. An additional important finding of our study is that Rho-kinase inhibitors induce a strong vasorelaxation and blood pressure reduction upon intravenous injection not only in hypertensive but in normotensive animals, as well. Inhibition of Rho-kinase represents a promising possibility to treat hypertension that is accompanied by endothelial dysfunction.

Calpains are a family of 14 intracellular calcium-dependent proteases, which have been implicated in cardiovascular diseases. We aimed to analyze specifically the expressional regulation of the different calpain isoforms in hypertensive target organ damage. Using real-time PCR, we found calpain 6 and 9 down-regulated by more than 50% and the endogenous calpain inhibitor calpastatin up-regulated by 225%, respectively, in the hearts of Dahl salt-sensitive rats on a high salt (4% NaCl) compared to normal salt diet. On the protein level, calpain 9 but not calpastatin was regulated in the hypertensive target organs heart and kidney. Moreover, the myocardial expression of calpain 9 protein was inversely linked to left ventricular mass (r= -0.93, p<0.01), and renal expression of calpain 9 protein correlated inversely with albuminuria (r= -0.82, p<0.05). In the aorta, there was no regulation of calpain 9 on the protein level. We conclude that differential regulation of calpain 9 may play a role in hypertensive target organ damage.

The effects of the sodium-hydrogen (Na/H) exchange inhibitor cariporide (HOE642), on insulin sensitivity and vascular function were studied in the JCR:LA-cp rat and the db/db mouse. In the insulin-resistant rat, cariporide reduced fasting insulin levels (42%, P < 0.02) and insulin response in a meal tolerance test (50%, P < 0.01), indicating increased insulin sensitivity. The ACE inhibitor, ramipril, used as a reference agent, reduced the insulin response to the meal, but not fasting levels. The EC50 for acetylcholine-mediated relaxation of phenylephrine-precontracted aortic rings was significantly lower in cariporide-treated rats (P < 0.002), but not in ramipril-treated rats. Flow response of the coronary circulation to bradykinin was significantly greater in both cariporide- and ramipril-treated rats, (3-fold decrease in the EC50, P < 0.05). Cariporide-treated hearts were smaller, slower beating, with greater developed LVP. In the obese db/db mouse, chronic treatment with cariporide obviated vascular hypercontractility and improved endothelial function. Thus, cariporide had beneficial effects on the abnormal insulin metabolism and associated vascular dysfunction in the JCR:LA-cp insulin-resistant rat, which develops advanced cardiovascular disease and ischemic myocardial lesions. It also improved vascular function in a similar mouse model of insulin resistance. These effects were markedly greater than those of ramipril.

Chronic inhibition of Rho-kinase has been recently implicated in retardation of atherogenesis induced by high-fat diet in low-density lipoprotein receptor deficient (LDLR−/−) mice. However, it remains to be examined whether long-term Rho-kinase inhibition will reduce vascular dysfunction in this model. LDLR−/− mice on a high-fat diet were treated either with saline (LDLR−/−) or with the Rho-kinase inhibitor Fasudil (HA1077, 5-Isoquinolinesulfonyl homopiperazine, 100 mg/kg/day by gavage, LDLR−/− + Fasudil) for 10 weeks. Fasudil-treatment normalized endothelial function (measured by means of endothelium-dependent vasorelaxation) in LDLR−/− + Fasudil, to the level of controls (C57BL/6J). No tolerance toward Rho-kinase inhibition has been detected in Fasudil-treated animals. We conclude that long-term Rho-kinase inhibition normalizes endothelial function without development of tolerance.

AIMS/HYPOTHESIS:Renal accumulation of AGEs may contribute to the progression of diabetic nephropathy. We evaluated the effect of ramipril (a pure ACE inhibitor) and AVE7688 (a dual inhibitor of ACE and neutral endopeptidase) on renal accumulation of the advanced glycation end-product (AGE) 3-deoxyglucosone-imidazolone, carboxymethyllysine (CML) and pentosidine, and on clearance of CML in type 2 diabetes.METHODS:Male Zucker diabetic fatty rats (ZDF, Gmi-fa/fa) rats were treated from age 10 to 37 weeks with ramipril (1 mg.kg(-1).day(-1)), AVE7688 (45 mg.kg(-1).day(-1)) or without drug. Ramipril and AVE7688 reduced albuminuria by 30 and 90%, respectively.RESULTS:ZDF rats showed increased renal accumulation of the AGE subtypes 3-deoxyglucosone-imidazolone, pentosidine and CML by about 40, 55 and 55%, respectively compared with heterozygous, non-diabetic control animals at the age of 37 weeks. AVE7688 but not ramipril attenuated the renal accumulation of 3-deoxyglucosone-imidazolone, pentosidine and CML and improved CML clearance in ZDF rats. During glycation reactions in vitro, AVE7688 also demonstrated potent chelating activity and inhibited metal-catalysed formation of pentosidine and CML.CONCLUSIONS/INTERPRETATION:Improved AGE clearance and direct inhibition of AGE formation by chelation may contribute to reduced accumulation of renal AGEs and to the nephroprotective effects of vasopeptidase inhibition in type 2 diabetes.

The aim of this study was to assess the effects of the Na + –H + exchange inhibitor cariporide on left ventricular (LV) morphology and function as well as inflammation in rabbits with heart failure. Rabbits with myocardial infarction (MI) and sham controls were randomized to receive either standard chow or chow supplemented with cariporide for 9 weeks. LV morphology was determined by echocardiography. LV systolic and diastolic function was assessed under load‐dependent and ‐independent conditions by analysis of LV pressure–volume loops using piezo‐electric crystals. Plasma concentrations of C‐reactive protein and aldosterone were measured. Rabbits with MI developed LV dilatation that was reduced by cariporide. Systolic and diastolic LV function was impaired in rabbits with MI when compared to sham, as indicated by a decreased d P /d t max (MI: 3537±718 mmHg s −1 , sham: 5839±247 mmHg s −1 , P <0.05), the load‐independent preload recruitable stroke work (PRSW)(MI: 22±7 mmHg, sham: 81±23 mmHg, P <0.05) and a reduction in the time constant of relaxation tau ( τ ) (MI: 27±1 ms, sham: 17±1 ms, P <0.05), and significantly improved by cariporide (d P /d t max : 4586±374 mmHg s −1 , PRSW: 67±18 mmHg, τ : 20±2 ms; P <0.05 vs MI/control). Induction of MI was associated with an increase in aldosterone and CRP, indicating activation of the neurohormonal and the inflammatory system that were largely reduced by cariporide. Cariporide improves LV morphology and function post MI and suppresses inflammation and neurohormonal activation in congestive heart failure (CHF). Na + –H + exchange inhibition may represent a new pharmaceutical approach for the treatment of CHF. British Journal of Pharmacology (2004) 142 , 1147–1154. doi: 10.1038/sj.bjp.0705746

Kv1.5 channels conduct the ultrarapid delayed rectifier current (IKur) that contributes to action potential repolarization of human atrial myocytes. Block of these channels has been proposed as a treatment for atrial arrhythmias. Here we report a novel and potent inhibitor of Kv1.5 potassium channels, N-benzyl-N-pyridin-3-yl-methyl-2-(toluene-4-sulfonylamino)-benzamide hydrochloride (S0100176), which exhibits features consistent with preferential block of the open state. The IC50 of S0100176 for Kv1.5 expressed in Xenopus oocytes was 0.7 μm. Ala-scanning mutagenesis within the pore helix and the S6 segment, regions that form the walls of the central cavity, was combined with voltage clamp analysis to identify point mutations that altered drug affinity. This approach identified Thr-479, Thr-480, Val-505, Ile-508, and Val-512 as the most important residues for block by S0100176. Mutations of these key residues to Ala or other amino acids caused marked changes in the IC50 of S0100176 (p < 0.01). For example, the IC50 of S0100176 increased 362-fold for T480A, 26-fold for V505A, 150-fold for I508A, and 99-fold for V512A. We used modeling to dock S0100176 into the inner cavity of a Kv1.5 pore homology model that was generated based on the crystal structure of KcsA. The docking predicted that the five residues identified by the Ala scan were positioned less than 4.5 Å from the compound. Based on the homology models, the positions of the five amino acids identified to interact with S0100176 face toward the central cavity and overlap with putative binding sites for other blockers and voltage-gated potassium channels.

Kv1.5 channels conduct the ultrarapid delayed rectifier current (IKur) that contributes to action potential repolarization of human atrial myocytes. Block of these channels has been proposed as a treatment for atrial arrhythmias. Here we report a novel and potent inhibitor of Kv1.5 potassium channels, N-benzyl-N-pyridin-3-yl-methyl-2-(toluene-4-sulfonylamino)-benzamide hydrochloride (S0100176), which exhibits features consistent with preferential block of the open state. The IC50 of S0100176 for Kv1.5 expressed in Xenopus oocytes was 0.7 microm. Ala-scanning mutagenesis within the pore helix and the S6 segment, regions that form the walls of the central cavity, was combined with voltage clamp analysis to identify point mutations that altered drug affinity. This approach identified Thr-479, Thr-480, Val-505, Ile-508, and Val-512 as the most important residues for block by S0100176. Mutations of these key residues to Ala or other amino acids caused marked changes in the IC50 of S0100176 (p<0.01). For example, the IC50 of S0100176 increased 362-fold for T480A, 26-fold for V505A, 150-fold for I508A, and 99-fold for V512A. We used modeling to dock S0100176 into the inner cavity of a Kv1.5 pore homology model that was generated based on the crystal structure of KcsA. The docking predicted that the five residues identified by the Ala scan were positioned less than 4.5 A from the compound. Based on the homology models, the positions of the five amino acids identified to interact with S0100176 face toward the central cavity and overlap with putative binding sites for other blockers and voltage-gated potassium channels.

The purpose of the study was to characterize the ionic and molecular mechanisms in the very early phases of electrical remodeling in a rabbit model of rapid atrial pacing (RAP). Long-term atrial fibrillation reduces L-type Ca2+(ICa,L) and transient outward K+(Ito) currents by transcriptional downregulation of the underlying ionic channels. However, electrical remodeling starts early after the onset of rapid atrial rates. The time course of ion current and channel modulation in these early phases of remodeling is currently unknown. Rapid (600 beats/min) right atrial pacing was performed in rabbits. Animals were divided into five groups with pacing durations between 0 and 96 h. Ionic currents were measured by patch clamp techniques; messenger ribonucleic acid (mRNA) and protein expression were measured by reverse transcription-polymerase chain reaction and Western blot, respectively. L-type calcium current started to be reduced (by 47%) after 12 h of RAP and continued to decline as pacing continued. Current changes were preceded or paralleled by decreased mRNA expression of the Ca2+channel β subunits CaB2a, CaB2b, and CaB3, whereas significant reductions in the α1subunit mRNA and protein expression began 24 h after pacing onset. Transient outward potassium current densities were not altered within the first 12 h, but after 24 h, currents were reduced by 48%. Longer pacing periods did not further decrease Ito. Current changes were paralleled by reduced Kv4.3 mRNA expression. Kv4.2, Kv1.4, and the auxiliary subunit KChIP2 were not affected. L-type calcium current and Itoare reduced in early phases of electrical remodeling. A major mechanism appears to be transcriptional downregulation of underlying ion channels, which partially preceded ion current changes.

The myocardial Na + /H + exchanger isoform 1 (NHE-1) represents a major H + extrusion mechanism for intracellular pH (pH i ) regulation especially during ischaemia and early reperfusion. Paradoxically, however, its activation contributes to induction of cell injury because Na + /H + exchange is coupled closely to elevations in intracellular [Ca 2+ ] through the Na + /Ca 2+ exchanger. NHE-1 is exquisitely sensitive to intracellular acidosis but other factors may have also stimulatory effects via phosphorylation-dependent processes, like autocrine and paracrine agents as well as hormonal factors such as endothelin-1, angiotensin II and α-1-adrenoceptor agonists. In addition, phosphorylation-independent NHE-1 activation mechanisms are known, e.g. cell shrinkage. To date at least 8 NHE isoforms have been identified and designated as NHE-1–8. All, except NHE-6 and NHE-7, which are located intracellularly, are restricted to the sarcolemmal membrane. The NHE-1 subtype is the predominant isoform in the heart, but NHE-6 is also expressed in the heart. Newly developed, selective NHE-1 inhibitors possess potent cardioprotective properties. The efficacy of NHE-1 inhibitors in experimental studies with ischaemia/reperfusion has led to clinical trials for the evaluation of these agents in high-risk patients with coronary artery disease (GUARDIAN Trial) and acute myocardial infarction (ESCAMI Trial). The GUARDIAN trial demonstrated only for the coronary artery by-pass graft (CABG) patient population a reduction in the primary cardiovascular endpoint (death and reoccurring myocardial infarction). However, recent evidence also suggests that NHE-1 inhibition may be conducive to attenuation of remodelling processes after myocardial infarction, independently of infarct size reduction and blood pressure. In addition, in separate preclinical studies, the NHE-1 inhibitor cariporide also prevented and/or caused regression of age-related and hypertension-induced myocardial fibrosis and hypertrophy. NHE-1 inhibitors thus offer substantial promise for clinical development for attenuation of both a) acute responses to myocardial injury, b) chronic post-infarct and hypertension- and age-related responses resulting in the development of heart failure.

Pharmazie in unserer ZeitVolume 32, Issue 1 p. 18-22 Pharmakologie Pharmakologische Grundlagen der Wirkung von ACE-Hemmern: Eingriff in Renin-Angiotensin-und Kallikrein-Kininsystem Wolfgang Linz Priv. Doz. Dr., Wolfgang Linz Priv. Doz. Dr.Search for more papers by this authorAndreas E. Busch Prof. Dr., Andreas E. Busch Prof. Dr. Andreas.Busch@aventis.com Vice President, Aventis Pharma Deutschland GmbH, Gebäude G 879, 65926 Frankfurt am Main, Tel.: 069/305-13547, Fax: 069/305-16393Search for more papers by this author Wolfgang Linz Priv. Doz. Dr., Wolfgang Linz Priv. Doz. Dr.Search for more papers by this authorAndreas E. Busch Prof. Dr., Andreas E. Busch Prof. Dr. Andreas.Busch@aventis.com Vice President, Aventis Pharma Deutschland GmbH, Gebäude G 879, 65926 Frankfurt am Main, Tel.: 069/305-13547, Fax: 069/305-16393Search for more papers by this author First published: 13 January 2003 https://doi.org/10.1002/pauz.200390002AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Volume32, Issue1Januar 2003Pages 18-22 RelatedInformation

Trotz erheblicher Fortschritte in der medikamentösen Therapie des Bluthochdrucks und der Herzinsuffizienz ist die mit diesen Erkrankungen verbundene Morbidität und Mortalität weiter hoch. Es gibt eine Vielzahl von innovativen Therapieansätzen, die sich in verschiedenen Stadien der klinischen Entwicklung befinden. Auffällig ist der enttäuschende Ausgang der jüngsten Studien mit Therapieprinzipien, die eine additive Hemmung der neuroendokrinen Aktivierung zusätzlich zu den etablierten Therapieoptionen zum Ziel haben. Die fehlende zusätzliche Wirksamkeit dieser neuen Substanzen hat zu der Hypothese geführt, dass die neuroendokrine Hemmung bei der Herzinsuffizienz bereits heute zu einem praktisch maximalen Therapieeffekt führt, der nicht weiter steigerbar ist, zumal mit jeder zusätzlichen Substanz eine weitere Senkung des Blutdrucks verbunden ist. Auch wenn diese Hypothese derzeit nicht als gesichert gelten kann, so scheinen doch diejenigen innovativen Therapieprinzipien einen besonderen Reiz zu haben, die außerhalb der neuroendokrinen Aktivierung angreifen und möglichst blutdruckneutral wirken.

Coexpression of KCNQ2 and KCNQ3 channels results in a 10‐fold increased current amplitude compared to that of KCNQ2 alone, suggesting the formation of heteromultimeric channels. There is no interaction of either channel with KCNQ1. We evaluated the C‐terminus as a potential interaction domain by construction of chimeras with interchanged C‐termini of KCNQ1, KCNQ2 and KCNQ3 and functional expression in Xenopus oocytes. The chimera of KCNQ1 with a KCNQ2 C‐terminus (Q1ctQ2) showed an 8‐fold increase in current amplitude, and Q1ctQ3 a 3‐fold increase when coexpressed with KCNQ3 and KCNQ2, respectively, indicating that the C‐terminus contains an interaction domain. To characterize this interacting region, we studied further chimeras of KCNQ1 containing different parts of the KCNQ3 C‐terminus for interaction with KCNQ2. We also evaluated short sequences of the KCNQ2 C‐terminus for a dominant‐negative effect on Q1ctQ3. According to the results of these experiments, functional interaction of KCNQ2 and KCNQ3 requires a highly conserved region of about 80 amino acids, previously called the A‐domain, plus either 40 residues downstream of the A‐domain (B‐domain) or the proximal C‐terminus between S6 and the A‐domain. Furthermore, the chimeras Q1ctQ3 and Q2ctQ3 showed > 10‐fold increased current amplitudes compared to KCNQ1 or KCNQ2 alone and a strong depolarizing shift of voltage‐dependent activation. The proximal part of the KCNQ3 C‐terminus was necessary to produce these effects. Our results indicate that specific parts of the C‐terminus enable the interaction between KCNQ2 and KCNQ3 channels and that different parts of the KCNQ3 C‐terminus are important for regulating current amplitude.

Blockade of the renin-angiotensin-aldosterone system may be beneficial in the management of hypertension. Consequently, several dual ACE/NEP inhibitors, such as M100240, are in development for the treatment of this condition. The effects of M100240 on blood pressure and heart rate in spontaneously hypertensive rats were evaluated. The study group comprised 5 male rats (Okamoto strain, 14-15 weeks old). Each animal was dosed once-daily, successively for 7 days, with placebo followed by 3, 10, and 30 mg/kg M100240 administered orally in solution. Telemetric measurements of blood pressure (BP) and heart rate (HR) were performed using a transmitter placed in each rat's peritoneal cavity and a receiver positioned below each cage. On Day 1, all of the doses of M100240 induced delayed, but statistically significant, decreases in both systolic (SBP) and diastolic arterial pressures (DBP) compared with baseline (p≤0.05) (Table). At doses of 10 and 30 mg/kg, decreases below the baseline values were maintained throughout the 7-day treatment period. No significant differences in BP measurements between placebo and 3 mg/kg M100240 treatment were seen after Day 1. At 10 and 30 mg/kg, there was an increase in HR after dosing, but this was only transient (for up to 2 hours on Day 1 (p≤0.01), and up to 3 hours on Day 7 (p≤0.05)). No other effects of clinical significance were observed. These results suggest that M100240, administered once daily, is capable of producing antihypertensive effects without long-lasting consequences for heart rate. Table. Changes in BP on day 1, as a percentage of predose values (%). At doses of 10 and 30 mg/kg, reductions in BP were maintained across the 7-day treatment period. SBP, systolic arterial pressure; DBP, diastolic arterial pressure; h, hours postdose.

The inhibitory effects of the anesthetic barbiturate pentobarbital on the slow (I Ks) and fast component (I Kr) of cardiac delayed rectifier potassium currents (I K) and on the inward rectifier potassium currents (I K1) were examined in Xenopus oocytes expressing the human minK, human ether-á-go-go related gene (HERG) and guinea pig Kir2.2, respectively. Block of native I K (I Ks and I Kr) and inward rectifier potassium current (I K1) by pentobarbital was examined in guinea pig ventricular myocytes.