Role of angiotensin II in the altered renal function of congestive heart failure.

Glomerular and tubule functions were assessed by micropuncture in rats with extensive myocardial infarction produced by ligation of the left coronary artery 4 weeks prior to study. When compared to sham-operated control rats, rats with myocardial infarction involving 40 +/- 4% of the left ventricular circumference had lower mean arterial pressure (96 +/- 5 vs. 122 +/- 4 mm Hg, P less than 0.005), and higher left ventricular end-diastolic pressure (24 +/- 3 vs. 5 +/- 0 mm Hg, P less than 0.001). Renal cortical microcirculatory dynamics of rats with myocardial infarction were characterized by reduced glomerular plasma flow rate (75 +/- 8 vs. 165 +/- 17 nl/min, P less than 0.005), but a proportionately lesser decline in single nephron glomerular filtration rate (28.0 +/- 2.8 vs. 41.7 +/- 3.1 nl/min, P less than 0.025), accounting for the observed rise in single nephron filtration fraction (0.38 +/- 0.02 vs. 0.25 +/- 0.02, P less than 0.005). These renal hemodynamic alterations in myocardial-infarcted rats were accompanied by a striking elevation in efferent arteriolar resistance (3.03 +/- 0.31 vs. 0.95 +/- 0.16 X 10(10) dyn X sec X cm-5, P less than 0.001). In addition, fractional proximal fluid reabsorption, assessed by end-proximal tubule fluid-to-plasma inulin concentration ratio, was elevated (2.21 +/- 0.12 vs. 1.64 +/- 0.09, P less than 0.025). The intravenous infusion of teprotide, an angiotensin I-converting enzyme inhibitor, led to the return of glomerular plasma flow rate, single nephron filtration fraction, single nephron glomerular filtration rate, efferent arteriolar resistance, and fractional proximal fluid reabsorption in myocardial-infarcted rats to, or toward, the levels found in control rats.(ABSTRACT TRUNCATED AT 250 WORDS)