Modification of experimental renal hypertension in the rat by indomethacin and hydralazine

The effects of pretreatment with l, H, and a combination, Hl, were assessed in rats made hypertensive by LRA. SBP, PRA, and urinary sodium and potassium excretion were measured 7 days and 1 day before LRA and 2 and 7 days after LRA on a fixed sodium diet. SBP increased 2 days after LRA in C rats, l- and Hl-treated rats but not in H-treated rats. The elevation of SBP was higher in the l group than in the C group. Hl showed a greater increase than H but less than C. PRA levels did not correlate with changes in SBP. PRA first increased 7 days after LRA. A highly significant decrease in sodium and potassium excretion was observed 7 days after LRA in C and l-treated rats. The data suggest that hydralazine may control blood pressure in this model by preventing sodium retention or, alternatively, that it may reduce blood pressure by direct peripheral vasodilation. Since natriuresis and vasodilation are two well-known effects of PGs, the results are compatible with the possibility that l exerted its noxious effect by inhibiting the synthesis of these compounds. It is also suggested by these studies that the renin angiotensin system does not play a central role in the acceleration of hypertension after l administration.