Dietary protein intake conditions the degree of renal vasoconstriction in acute renal failure caused by ureteral obstruction.

Whole kidney inulin (CIn) and PAH (CPAH) clearances were measured after unilateral release of bilateral ureteral obstruction (BUO) of 24-h duration in rats fed for 4 wk isocaloric diets containing either 40% casein (high protein diet) or 6% casein (low protein diet). Values for CIn and CPAH were markedly depressed in both groups but to a greater extent in high protein-fed rats, averaging less than 60% of values measured in low protein-fed animals. Captopril, an inhibitor of the angiotensin I converting enzyme, increased CIn and CPAH markedly but comparably in high or low protein fed rats. Micropuncture studies performed after unilateral release of BUO in another group of rats fed a high or a low protein diet revealed lower levels of glomerular plasma flow rate (QA) and single nephron glomerular filtration rate (SNGFR) in rats fed a high protein diet. Values for renal arteriolar resistances were nearly twofold in high as compared with low protein-fed animals. Infusion of OKY-1581, an inhibitor of thromboxane A2 synthetase, increased both QA and SNGFR, decreased arteriolar resistances, and increased glomerular capillary ultrafiltration coefficient in high but not in low protein-fed rats. Urinary thromboxane B2 excretion per milliliter of GFR was greater in rats fed a high protein diet than in those fed a low protein diet after release of BUO but not in normal rats. In normal rats infusion of OKY-1581 did not increase CIn or CPAH.(ABSTRACT TRUNCATED AT 250 WORDS)