Chronic angiotensin converting enzyme inhibition in the two-kidney, one clip hypertensive rat

ACE inhibition actively promotes cell survival by altering gene expression

We tested the effect of ACE inhibition on the survival of bovine retinal (REC) and choroidal (CEC) endothelial cells (EC) in culture. The ACE inhibitor captopril delayed the apoptotic tube collapse of REC on Matrigel for >15 days. Captopril treatment of confluent monolayers (2-8 weeks) followed by slow starvation (2-4 weeks) increased EC viability by approximately 200%. Two-week captopril exposures were sufficient to confer maximal protection. Only vehicle-treated EC demonstrated apoptotic features such as membrane blebbing and DNA laddering. By RT-PCR, the starvation marker p202 was upregulated only in starved cells. In REC, captopril upregulated the pro-survival proteins mortalin-2, uPA, and uPAR while downregulating the anti-growth sprouty-4 and tPA. In CEC, captopril also upregulated tPA and its inhibitor PAI-1. Amiloride (uPA inhibitor) blocked the captopril-induced increase in EC survival, secondary sprouting, and invasion in Matrigel. The pro-survival effects of captopril involve the reprogramming of genes involved in cell survival and immortalization.

The effects of dietary potassium on vascular and glomerular lesions in hypertensive rats

The present study examines the effects of dietary potassium (K) on hypertensive glomerular and vascular lesions in deoxycorticosterone acetate and salt induced (DOCA-salt) and two kidney one clip (2K1C) hypertensive as well as normotensive control rats. Animals received a regular (0.28% K), high (1.1% K) or low (0.07% K) potassium diet for 6 weeks. In control rats, low K diet significantly increased systolic blood pressure (SBP) (p < 0.05). In DOCA-salt rats, high K diet did not modify SBP or glomerular and vascular lesions while low K diet significantly increased premature death in these rats. In 2K1C rats, dietary K did not alter the blood pressure, but percentage media area (% media) of intramyocardial arteries, percentage of glomerular lesions, and renal arterial and arteriolar lesion scores were lower in high K diet rats than regular and low K diet rats (p < 0.05). This study is the first demonstration that high K diet can protect against vascular and glomerular lesions in a non salt-loaded hypertensive model. The beneficial effects of dietary K on vascular lesions are at least in part independent of changes in blood pressure, and may be renin related.

Continuous versus intermittent angiotensin converting enzyme inhibition in renal hypertensive rats

Converting enzyme inhibitors impair renal function of the kidney beyond a stenosis of the renal artery in humans and induce histological lesions in the clipped kidney of renal hypertensive rats. In two-kidney, one clip hypertensive rats, we compared the time course and magnitude of the biochemical effects of angiotensin converting enzyme inhibition on the plasma renin-angiotensin system, cardiac hypertrophy, renal lesions, and 24-hour blood pressure decrease induced by either intermittent angiotensin converting enzyme inhibition administration (benazepril PO, 10 mg/kg once a day, n = 93) or continuous administration (benazeprilat, 3 mg/kg per day via osmotic pumps, n = 92). Control rats (n = 91) received the drug vehicle intermittently or continuously. Mortality was significantly reduced by both intermittent (n = 3/93) and continuous (n = 3/92) inhibition compared with controls (n = 18/91) (P < .001). Changes in the plasma renin-angiotensin system and blood pressure were parallel. A continuous suppression of the activity of the plasma renin-angiotensin system was associated with a 24-hour decrease in blood pressure with continuous inhibition, whereas intermittent inhibition induced a similar fall in blood pressure only for the first hours after gavage.(ABSTRACT TRUNCATED AT 250 WORDS)

Preservation of renal function by angiotensin during chronic adrenergic stimulation

The purpose of the present study was to determine the role of angiotensin II (Ang II) in mediating renal responses to chronic intrarenal norepinephrine infusion. Norepinephrine was continuously infused for 5 days into the renal artery of unilaterally nephrectomized dogs at progressively higher daily infusion rates: 0.05, 0.10, 0.20, 0.30, and 0.40 micrograms/kg/min. In three additional groups of dogs, norepinephrine infusion was repeated during chronic intravenous captopril administration to fix plasma Ang II concentration at 1) low levels (no Ang II infused), 2) high levels in the renal circulation (Ang II infused intrarenally at a rate of 1 ng/kg/min), and 3) high levels in the systemic circulation (Ang II infused intravenously at a rate of 5 ng/kg/min). In the control group of animals with intact renin-angiotensin systems, there were progressive increments in mean arterial pressure (from 96 +/- 4 to 141 +/- 6 mm Hg) and plasma renin activity (from 0.4 +/- 0.1 to 10.9 +/- 4.5 ng angiotensin I/ml/hr) and concomitant reductions in glomerular filtration rate and renal plasma flow to approximately 40% of control during the 5-day norepinephrine infusion period. In marked contrast, when captopril was infused chronically without Ang II, mean arterial pressure was 20-25 mm Hg less than that under control conditions, and the renal hemodynamic effects of norepinephrine were greatly exaggerated; by day 3 of norepinephrine infusion, both glomerular filtration rate (16 +/- 2% of control) and renal plasma flow (12 +/- 4% of control) were considerably lower than values in control animals (86 +/- 4% and 80 +/- 8% of control, respectively). Similarly, when a high level of Ang II was localized in the renal circulation during captopril administration, mean arterial pressure was depressed, and again there were pronounced renal responses to norepinephrine. Conversely, when Ang II was infused intravenously during captopril administration, mean arterial pressure was not reduced, and the glomerular filtration rate and renal plasma flow responses to norepinephrine were similar to those that occurred under control conditions. These findings indicate that the renin-angiotensin system prevents exaggerated renal vascular responses to chronic norepinephrine stimulation by preserving renal perfusion pressure.