Effects of atenolol and enalapril on blood pressure, plasma renin activity and urinary prostanoids.

In order to assess whether blood pressure reduction with atenolol or enalapril is associated with changes in renal prostaglandin (PG) synthesis, we studied the effects of 10 weeks therapy in 20 subjects with mild or moderate hypertension. After a four week placebo run-in period, subjects were randomized to receive either atenolol 50-100 mg/day or enalapril 5-20 mg/day for 10 weeks, then crossed over to the alternate active drug. Both drugs lowered blood pressure: placebo 147/97, atenolol 135/87, enalapril 132/87 (p less than 0.05, for both). Atenolol reduced resting heart rate but neither drug changed body weight, serum sodium or potassium or creatinine clearance. Intravenous furosemide was used as a standardized stimulus of renal PG synthesis. Neither drug changed the excretion rates of 6ketoPGF1 alpha or thromboxane B2 (hydrolysis products of PGI2 and thromboxane A2 respectively). Diuretic, kaliuretic, and natriuretic effects of furosemide were also not affected. Plasma renin activity was increased by enalapril but reduced slightly by atenolol. Subjects with more marked blood pressure reduction showed responses to furosemide no different than those with less effect. We conclude that blood pressure reduction with atenolol or enalapril does not change the response of renal eicosanoid synthesis to acute stimulation with furosemide.