An examination of chronic angiotensin-converting enzyme inhibition in the rat

We have examined the systemic and renal effects of 2 weeks' administration of angiotensin-converting enzyme inhibition (CEI) to both normal and chronic NaCl-depleted Munich-Wistar rats and focused particularly on the factors contributing to the significant hypotension observed during surgery and anesthesia and the response of renal glomerular hemodynamics under these conditions. At renal micropuncture, mean arterial pressure was decreased in rats receiving CEI on normal and NaCl-depleted diets (72 +/- 5 and 78 +/- 6 mm Hg, p less than 0.01) but nephron filtration rate (sngfr) was well maintained since plasma flow was not altered and glomerular capillary pressure only slightly decreased. Negative Na+ balance in NaCl-depleted CEI rats correlated with decreased awake blood pressures. Under surgery, plasma norepinephrine and epinephrine were not increased in CEI rats in spite of hypotension, and diminished adrenergic responses may contribute to systemic and renal effects observed. Nephron plasma flow and sngfr are remarkably well preserved during CEI in spite of hypotension due to marked afferent arteriolar dilation.