Effects of propranolol on development and maintanance of severe renal hypertension in rats.

1. The effect of chronic administration of propranolol on the development and maintenance of severe renal hypertension in rats subjected to unilateral renal artery constriction was studied in relation to possible changes in peripheral PRA and the blood and tissue levels of propranolol. Propranolol was administered s.c. twice daily in doses of 1, 10 and 25 mg/kg, starting 2 days before operation. 2. Contrary to expectations, not only did the initial rise in systolic blood pressure become accelerated, but the established level of hypertension attained in the propranolol treated rats was of the same severity as that attained in placebo treated rats. Moreover, the progressive rise in peripheral plasma renin activity following unilateral renal artery constriction was not affected by propranolol administration. 3. The same doses of propranolol were also administered daily for 8 days to rats with established severe hypertension. A slight further rise in blood pressure occurred initially, followed by a moderate decrease of 15-25 mmHg. Propranolol failed to exert this minor hypotensive effect in hypertensive rats treated concomitantly with furosemide. No suppressive effect on the markedly increased levels of plasma renin activity was observed in these severely hypertensive rats in the presence or absence of furosemide administration. 4. These results indicate that in severely renal hypertensive rats propranolol has only a minor hypotensive effect and no blocking action on renin release under the conditions of study.