Perinephritis hypertension in Macaca fascicularis (cynomolgus monkey): studies of the renin-angiotensin-aldosterone axis and renal hemodynamic function.

The purpose of the present study was to characterize the etiology of bilateral perinephritis hypertension in the non-human primate. Hypertension was induced in female cynomolgus (Macaca fascicularis) monkeys by wrapping both kidneys under sterile surgical procedures. Mean arterial pressure (MAP), plasma renin activity (PRA), plasma aldosterone concentration (ALDO), para-aminohippurate (PAH) clearance, glomerular filtration rate (GFR), urine volume, and sodium and potassium excretion were measured before and weekly after induction of the hypertension. MAP increased progressively from 108 +/- 1 to 135 +/- 4 mmHg during the first 6 weeks; thereafter, MAP remained at this elevated level, PRA was elevated two- to fivefold for up to 10 weeks after the hypertension and ALDO was elevated during 1 (139%), 4 (60%), 6 (196%), 8 (249%) and 10 (148%) weeks of the hypertension. PAH clearance and GFR were significantly reduced during week 1 of the hypertension, but returned to control values by week 2. Urine volume was increased significantly during the first week of the hypertension, while sodium and potassium excretion were not changed. Captopril (15 mumol/kg, intravenously) normalized the blood pressure regardless of the severity or duration of the disease. Additionally, captopril lowered ALDO and increased PRA. It is concluded that bilateral perinephritis hypertension in the monkey is dependent on increased activity of the renin-angiotensin-aldosterone axis.

Pharmacology of novel imidazole alcohol inhibitors of primate renin.

SQ 30,774 and SQ 31,844 are representatives of a novel class of renin inhibitors, the imidazole alcohols. These compounds, which contain an imidazole ring as part of their active site binding group are potent in vitro inhibitors of primate renin, but not rat, hog of dog renin. In conscious, sodium-depleted cynomolgus monkeys both compounds produced a dose-related inhibition of plasma renin activity (PRA) at doses ranging between 0.001 and 1.0 mumol/kg, intravenously, and total inhibition was observed after the highest dose. However, a reduction in blood pressure was observed only after an intravenous dose of 10 mumol/kg or when the compounds were administered by infusion. In sodium-replete monkeys, SQ 30,774 inhibited the rise in arterial pressure and PRA following administration of exogenous monkey renin. When the compounds were administered orally at 50 mumol/kg, only SQ 31,844 significantly inhibited PRA (80%). It is concluded that representatives of the imidazole alcohol class of renin inhibitors are potent inhibitors of renin in vitro and inhibit PRA and lower arterial pressure in vivo.

Comparisons in vitro, ex vivo, and in vivo of the actions of seven structurally diverse inhibitors of angiotensin converting enzyme (ACE).

1. Seven drugs (captopril, zofenopril, enalapril, ramipril, lisinopril, fosinopril, and SQ 29,852) were compared in vitro in homogenates of aorta, brain, heart, lung, and kidney and in sera of spontaneously hypertensive rats (SHR) both with respect to potencies of their active moieties as inhibitors of angiotensin-converting enzyme (ACE), and, where applicable, rates of hydrolysis of their prodrug ester functions. 2. In ex vivo dose-response and time-course studies, the inhibitory effects of the seven drugs on tissue ACEs and their relative distributions to SHR tissues were compared following oral administration. 3. The relative potencies of the inhibitory moieties of the drugs (in parentheses) and the normalized 'equiactive' oral doses employed for time-course studies were: SQ 29,852 (1.0), 100 mg kg-1; captopril (3.5), 30 mg kg-1; enalapril (12), 20 mg kg-1; fosinopril (13), 25 mg kg-1; zofenopril (20), 10 mg kg-1; lisinopril (24), 10 mg kg-1; and ramipril (51), 5 mg kg-1. 4. Following oral administration of the drugs to SHR, the degree and duration of ACE inhibition in aorta and lung correlated with the antihypertensive actions, with ramipril, lisinopril, and zofenopril producing effects of the greatest magnitude and duration. 5. Ramipril and enalapril did not inhibit brain ACE ex vivo; captopril and zofenopril had modest but short-lasting effects; and fosinopril, lisinopril, and SQ 29,852 had long-lasting inhibitory actions, which, with the latter two, were delayed in onset. 6. All of the drugs produced significant inhibition of kidney ACE, with ramipril and fosinopril having somewhat weaker effects, perhaps due to biliary routes of excretion. 7. Captopril, fosinopril, and particularly zofenopril inhibited cardiac ACE ex vivo with degrees and durations that were marked compared with those of the other drugs; preliminary studies with isolated hearts suggest a possible relationship between inhibition of cardiac ACE and preservation of cardiac function subsequent to ischaemia.

Biology of a novel class of potent long-acting angiotensin converting enzyme inhibitors: the acyl lysinamido phosphonates.

The acyl lysinamido phosphonates represent a novel class of angiotensin I converting enzyme (ACE) inhibitors. Representatives of this class produce 50% inhibition of purified rabbit lung ACE at concentrations less than 8 nmol/l. After intravenous and oral administration to normotensive rats the phosphonates inhibited an angiotensin I pressor response by 50% at doses less than or equal to enalapril (oral studies) or its free acid, MK-422 (intravenous studies); however, the duration of effect was much longer after the phosphonates. In conscious cynomolgus monkeys, representatives of the phosphonate class showed greater inhibition of an angiotensin I pressor response and for a much longer period of time than enalapril, fosinopril and lisinopril. Similarly, in sodium-depleted monkeys the blood pressure lowering effects of enalapril, lisinopril and fosinopril were of short duration compared with those of the phosphonates. It is concluded that the acyl lysinamido phosphonates represent a potent and long-acting class of ACE inhibitors in vitro and in vivo.