Abstract
The influence of a diuretic, clorexolone and a β-adrenoceptor blocking agent, alprenolol, alone and in combination, on blood pressure, heart rate and serum angiotensin II and aldosterone levels were examined in 5 conscious renal hypertensive dogs. Clorexolone (10 mg/kg p.o., twice a day) caused a slight increase in heart rate, and a gradual decrease in blood pressure which became significant after the second day of treatment (p<0.05). The mean reduction in systolic blood pressure by clorexolone alone was about 15 mm Hg. Addition of alprenolol (10 mg/kg p.o., twice a day) induced a further rapid decrease in arterial blood pressure and there was a tendency toward decrease in the increased heart rate. The mean decrease in systolic blood pressure was about 26 mm Hg and such was highly significant in comparison with that exerted by clorexolone alone (p<0.025). After withdrawal of clorexolone and final replacement of alprenolol with lactose, the decreased blood pressure gradually returned to the initial value. Increases in serum angiotensin II and aldosterone levels seen after clorexolone alone declined to the initial value when alprenolol was given in combination with clorexolone. The antihypertensive effect of this combination is attributed mainly to the inhibition of renin-angiotensin-aldosterone system, to decrease in circulating blood volume, and in part to decrease in the heart rate.
