Chronic effects of bunitrolol and pindolol on blood pressure, heart rate, vascular lesions, and plasma renin activity in hypertensive rats.

Bunitrolol (BNT) (1, 2) and pindolol (PDL) (3) are i9-adrenergic blocking drugs with intrinsic sympathomimetic activity. We determined the antihypertensive effect of BNT in hypertensive rats using PDL as the reference drug. The previous reports indicated that PDL is effective in spontaneously hyper tensive rats (SHR) (4-6), but not effective in deoxycorticosterone and salt (DOC) hyper tensive rats nor in two kidney, one clip hypertensive (CLIP) rats (4, 7). BNT and PDL were given orally at 50 and 30 mg/kg, per day, respectively, every day for 10 weeks in SHR, DOC, and CLIP rats. Tail blood pressure (BP) and heart rate (HR) were determined every week. At the end of the experiment, the mean BP was determined directly through a cannula inserted into the abdominal aorta. Plasma renin activity (PRA) was measured. Vascular lesions in the renal, cardiac, and mesenteric areas were examined. No antihypertensive effects of BNT and PDL were demonstrated in the three models of hypertensive rats except in the DOC hypertensive rats treated with PDL. SHR rats were female, 6 weeks of age, F34 from the colony of the Department of Pharmacology, Jichi Medical School, and they weighed 80-120 g. The drug treatments were started at 7 weeks of age, after the control observation for one week. DOC and CLIP hypertensions were made in female rats of HOS®: Donryu strain, 8-9 weeks of age, weighing 160-190 g, as reported