Metabolites of [(14)C]-5-(2-ethyl-2H-tetrazol-5-yl)-1-methyl-1,2,3, 6-tetrahydropyridine in mice, rats, dogs, and humans.
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The M1 muscarine agonist, 5-(2-ethyl-2H-tetrazol-5-yl)-1-methyl-1,2, 3,6-tetrahydropyridine (Lu 25-109), is extensively metabolized in mice, rats, dogs, and humans. The metabolite profile after an oral dose of [(14)C]Lu 25-109 was determined in plasma and in urine. Lu 25-109 was metabolized by N-demethylation (Lu 25-077), N-oxidation (Lu 32-181), and N-deethylation (Lu 31-126). In addition, combined N-demethylation and N-deethylation (Lu 31-190), and formation of a pyridine derivative took place (Lu 31-102). Lu 25-109 was also oxidized to pyridinium (Lu 29-297), 3-hydroxy-pyridinium (Lu 35-080), N-deethyl-2-pyridone (Lu 35-026), and a glucuronide of a 4, 6-dihydroxy-pyridinium ("m/z 398") compounds. A glucuronide of a dihydroxylated dihydro-pyridine compound ("m/z 400") was isolated from human urine, but not fully identified. In vitro studies were undertaken to elucidate the order of formation of the metabolites. In human plasma, the concentrations of Lu 25-109 and the pharmacologically active N-demethyl metabolite (Lu 25-077) were small compared with the N-oxide (Lu 32-181) and the N-deethyl-2-pyridone (Lu 35-026) at the first sample time (0.75 h). The N-deethyl metabolite (Lu 31-126) was the major component in human plasma between 3 and 10 h postdose. The major human metabolites in urine (Lu 32-181, Lu 35-026, and Lu 31-126) and the minor metabolites (Lu 25-077, Lu 35-080, Lu 31-190, and Lu 29-297) were all present in urine from rats, dogs, and mice, whereas m/z 398 was present in only mice and humans, and Lu 31-102 in only rats. The minor human metabolite m/z 400 was not detected in mice, rats, or dogs. (+info)
The paradox of the low-renin state in diabetic nephropathy.
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Although diabetic nephropathy is often a low renin state, the renin system appears to be implicated in its pathogenesis. In this study, it was hypothesized that the low plasma renin activity (PRA) is misleading, masking and perhaps reflecting an activated intrarenal renin system. PRA and renal vascular responses (inulin and para-aminohippurate clearance) to graded doses of an angiotensin II (AngII) antagonist, irbesartan, were assessed in eight healthy volunteers and 12 patients with type 2 diabetes mellitus and nephropathy on a 10 mmol Na intake, to activate the renin system. Basal PRA was suppressed in type 2 diabetes mellitus compared with the healthy subjects (0.58 +/- 0.14 versus 1.58 +/- 0.28 ng/L per s, mean +/- SEM; P < 0.01). Despite the low PRA, renal perfusion rose more in response to irbesartan in type 2 diabetes mellitus (714 +/- 83 to 931 +/- 116 ml/min; P = 0.002) than normal (624 +/- 29 to 772 +/- 49 ml/min; P = 0.008). The youngest patients were hyperfiltrating and showed the largest rise in renal plasma flow in response to irbesartan, whereas renal plasma flow rose less and GFR fell in patients with low basal GFR. PRA rose in response to irbesartan more gradually in the patients with type 2 diabetes mellitus, but ultimately matched the normal response. To account for the apparent paradox of a heightened renal hemodynamic response to an AngII antagonist in the face of a low PRA in type 2 diabetes mellitus, and the rise in PRA following the AngII antagonist, it is proposed that there is increased intrarenal AngII production in type 2 diabetes mellitus. This increase could account for suppressed circulating renin, the exaggerated renal vasodilator response to irbesartan, and the therapeutic effectiveness of interrupting the renin system in diabetic nephropathy. (+info)
Blockade of central angiotensin AT(1) receptors improves neurological outcome and reduces expression of AP-1 transcription factors after focal brain ischemia in rats.
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BACKGROUND AND PURPOSE: Angiotensin-converting enzyme inhibitors have been shown to protect against stroke in hypertensive rats and to improve neurological outcome after cerebral ischemia in normotensive rats. The present study was designated to test the hypothesis that blockade of brain AT(1) receptors improves the recovery from focal cerebral ischemia and reduces expression of AP-1 transcription factors c-Fos and c-Jun, which have been associated with programmed cell death and neurodegeneration. METHODS: Experiments were carried out in normotensive male Wistar rats. Focal cerebral ischemia was induced by middle cerebral artery occlusion lasting for 90 minutes and followed by reperfusion. The selective AT(1) receptor antagonist irbesartan was infused intracerebroventricularly over a 5-day period before the induction of ischemia at a dose that inhibited brain but not vascular AT(1) receptors. Twenty-four hours after ischemia, neurological outcome was evaluated and expression of c-Fos and c-Jun proteins in the brain was studied immunocytochemically. RESULTS: Focal brain ischemia resulted in a strong induction of c-Fos and c-Jun proteins in the cortex, which positively correlated with the degree of neurological deficits. Treatment of rats with irbesartan significantly improved neurological outcome of focal cerebral ischemia when compared with the vehicle-treated group and markedly reduced the expression of c-Fos and c-Jun proteins in the cortex on the ligated side of the brain. Irbesartan pretreatment completely abolished the ischemia-induced c-Fos expression in the hippocampus. CONCLUSIONS: The present study shows a relationship between c-Fos and c-Jun expression and neurological outcome after focal brain ischemia. Our data indicate that long-term blockade of central AT(1) receptors improves the recovery from brain ischemia and reduces the expression of c-Fos and c-Jun proteins in the brain. Pretreatment with an AT(1) receptor antagonist has beneficial effects after cerebral ischemia. (+info)
Structure of the HIV-1 integrase catalytic domain complexed with an inhibitor: a platform for antiviral drug design.
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HIV integrase, the enzyme that inserts the viral DNA into the host chromosome, has no mammalian counterpart, making it an attractive target for antiviral drug design. As one of the three enzymes produced by HIV, it can be expected that inhibitors of this enzyme will complement the therapeutic use of HIV protease and reverse transcriptase inhibitors. We have determined the structure of a complex of the HIV-1 integrase core domain with a novel inhibitor, 5ClTEP, 1-(5-chloroindol-3-yl)-3-hydroxy-3-(2H-tetrazol-5-yl)-pro penone, to 2.1-A resolution. The inhibitor binds centrally in the active site of the integrase and makes a number of close contacts with the protein. Only minor changes in the protein accompany inhibitor binding. This inhibitor complex will provide a platform for structure-based design of an additional class of inhibitors for antiviral therapy. (+info)
Hypertension and endothelial dysfunction in apolipoprotein E knockout mice.
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Mice lacking ApoE (Apoe(-/-)) develop initially hypercholesterolemia and lastly atherosclerosis. This study examined hemodynamics and endothelial function in 6-week-old Apoe(-/-) mice with hypercholesterolemia only, 7.5-months-old Apoe(-/-) mice with both hypercholesterolemia and atherosclerosis, and age matched controls. One day after implantation of catheters into the carotid artery, arterial pressure was measured in conscious, unrestrained mice. Compared with the respective controls, there was a significant increase in arterial pressure and the ratio of left ventricular weight to body weight in 7.5-month-old Apoe(-/-) mice but not in 6-week-old Apoe(-/-) mice. Histopathological analysis demonstrated significant renal artery disease in the form of extensive atheromatous plaques only in 7.5-month-old Apoe(-/-) mice, whereas no atherosclerotic lesions were found in 6-week-old Apoe(-/-) mice. For evaluation of endothelial function, a laser Doppler perfusion imager with a computer-controlled optical scanner was used to measure cutaneous blood perfusion on the dorsal side of one hind paw before and after topical application of mustard oil, which is known to induce nitric oxide-mediated vasodilation. The mustard oil treatment elicited a substantial increase in blood perfusion (P<0.01), which was similar between 6-week-old Apoe(-/-) mice and controls but significantly blunted in 7.5-month-old Apoe(-/-) mice versus control mice, suggesting nitric oxide-mediated vasodilation is diminished in 7.5-month-old Apoe(-/-) mice but not in 6-week-old Apoe(-/-) mice. In contrast, the increase in blood perfusion induced by topical administration of cilostazol, which induces vasodilation via cyclic adenosine monophosphate, was not different between 7.5-month-old Apoe(-/-) mice and controls. Thus hypertension and endothelial dysfunction observed in 7.5-month-old Apoe(-/-) mice may be due mainly to atherosclerosis. (+info)
Role of AT(1) receptors and autonomic nervous system in mediating acute pressor responses to ANG II in anesthetized mice.
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Hemodynamic responses to angiotensin II and the role of AT(1) and AT(2) receptors and the autonomic nervous system in mediating acute responses to angiotensin II were investigated in anesthetized CD1 mice. Injections of angiotensin II caused dose-related increases in systemic arterial pressure that were antagonized by candesartan. Pressor responses to angiotensin II were not altered by PD-123,319 in doses up to 25 mg/kg iv. At the lowest dose studied (20 microgram/kg iv), the inhibitory effects of candesartan were competitive, whereas at the highest dose (100 microgram/kg iv) the dose-response curve for angiotensin II was shifted to the right in a nonparallel manner with inhibitory effects that could not be surmounted. The inhibitory effects of candesartan were selective and were similar in animals pretreated with enalaprilat (1 mg/kg iv) to reduce endogenous angiotensin II production. Acute pressor responses to angiotensin II were not altered by propranolol (200 microgram/kg iv), phentolamine (200 microgram/kg iv), or atropine (1 mg/kg iv) but were enhanced by hexamethonium (5 mg/kg iv). Increases in total peripheral resistance induced by angiotensin II were inhibited by the AT(1)-receptor antagonist but were not altered by AT(2)-, alpha-, or beta-receptor antagonists. These results suggest that acute pressor responses to angiotensin II are mediated by AT(1) receptors, are buffered by the baroreceptors, and are not modulated by effects on AT(2) receptors and that activation of the sympathetic nervous system plays little if any role in mediating rapid hemodynamic responses to the peptide in anesthetized CD1 mice. (+info)
AT(2) receptor stimulation enhances antihypertensive effect of AT(1) receptor antagonist in hypertensive rats.
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In the present study, we investigated the role of the angiotensin type 2 (AT(2)) receptor in the regulation of blood pressure in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). We tested the hypothesis that AT(2) receptor activation may contribute to the antihypertensive effects of angiotensin type 1 (AT(1)) receptor antagonists. Mean arterial pressure (MAP) and heart rate were measured over a 4-day protocol in various groups of rats that received the following drug combinations: the AT(1) receptor antagonist candesartan (0.01 or 0.1 mg/kg IV) alone, the AT(2) receptor agonist CGP42112 (1 microg/kg per minute) alone, and candesartan plus CGP42112. In both SHR and WKY, 4-hour infusions of saline and CGP42112 alone did not alter MAP. In WKY, both doses of candesartan alone caused small decreases in MAP, which were similar when combined with CGP42112. In SHR, candesartan (0.1 mg/kg) caused an immediate, marked decrease in MAP, which was unaffected when combined with CGP42112. By contrast, in separate SHR, a 10-fold lower dose of candesartan (0.01 mg/kg) caused a slower-onset depressor response, which was enhanced when combined with CGP42112. The involvement of AT(2) receptors was confirmed in another group of SHR, since this facilitation of the antihypertensive effect of candesartan by CGP42112 was abolished by the coinfusion of the AT(2) receptor antagonist PD123319 (50 microg/kg per minute) with the candesartan/CGP42112 combination. Collectively, these data suggest that in SHR, AT(2) receptor activation can facilitate the initial depressor response caused by an AT(1) receptor antagonist. (+info)
Improvement in exercise tolerance and symptoms of congestive heart failure during treatment with candesartan cilexetil. Symptom, Tolerability, Response to Exercise Trial of Candesartan Cilexetil in Heart Failure (STRETCH) Investigators.
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BACKGROUND: The renin-angiotensin system plays an important part in the pathogenesis of congestive heart failure (CHF). This study evaluated the effect of an angiotensin II type 1 receptor antagonist on exercise tolerance and symptoms of CHF. METHODS AND RESULTS: In this multicenter, double-blind, parallel-group study, 844 patients with CHF were randomized to 12 weeks' treatment with placebo (n=211) or candesartan cilexetil 4 mg (n=208), 8 mg (n=212), or 16 mg (n=213) after a 4-week placebo run-in period. Changes in exercise time, Dyspnea Fatigue Index score, NYHA functional class, and cardiothoracic ratio were determined. Candesartan cilexetil produced a dose-related improvement in exercise time. For the intention-to-treat population, the increase produced by candesartan cilexetil 16 mg was significantly greater than that produced by placebo (47.2 versus 30.8 seconds, P=0.0463). All doses of candesartan cilexetil significantly improved the Dyspnea Fatigue Index score relative to placebo. NYHA class improved more frequently in the candesartan cilexetil groups; the differences relative to placebo were not significant. The decrease in cardiothoracic ratio with candesartan 4 to 16 mg was small but statistically significant compared with placebo (all P<0.05). In all candesartan cilexetil groups, plasma renin activity and angiotensin II levels increased from baseline and aldosterone levels decreased in the 8- and 16-mg treatment groups. Candesartan cilexetil was well tolerated at all doses. CONCLUSIONS: In summary, treatment with candesartan cilexetil demonstrated significant improvements in exercise tolerance, cardiothoracic ratio, and symptoms and signs of CHF and was well tolerated. (+info)