Initial mechanisms in hypertension after bilateral renal ischemia in the rat.

Cumulative water- and electrolyte balance, plasma creatinine (PC), plasma renin activity (PRA), urinary prostaglandins (PGs) E2, and F2alpha and kallikrein (K) were studied in 40 male Wistar CHbb THOM rats (250 +/- 4 g SE). A solid silver clip (0.25 mm lumen) was applied to both renal arteries in 18 animals; 13 rats were sham-operated and nine remained intact. The analyses were performed during a control period and up to 10 days after surgery. Blood pressure (BP) recorded on the 10th and 12th day of the study increased significantly in clipped rats with respect to sham rats (p less than 0.001);PC and PRA measured on the 11th day were not significantly different. A positive cumulative water "balance" )p less than 0.01) and sodium balance (p less than 0.02) was found in clipped rats when compared with sham rats in the first 5 days of the experimental period. Significantly higher values of PGE2 urinary excretion were observed in sham rats vs clipped rats on the 2nd and 5th day after surgery (p less than 0.02). On the 2nd day after surgery, K urinary excretion was significantly lower in clipped rats than in sham rats (p less than 0.02). No significant changes were observed in PGF2alpha excretion. The absence of significant difference in PRA 10 days after bilateral renal artery stenosis points to a lack of any fundamental role of circulating angiotensin II at this stage of the development of hypertension. The significant water- and salt retention in the first 5 days after clipping suggests that it might be involved in the pathogenesis of this model. Early changes in PGs E2 and F2alpha and K appear to be related more to intrarenal adjustments soon after surgery than to the increase in BP.