Acute renal effects of doxazosin in man

To evaluate the role of alpha 1-adrenoceptors in the regulation of renal blood flow and renin secretion, we infused doxazosin in incremental doses (group I, n = 5) or at a fixed rate of 1 microgram kg-1 min-1 (group II, n = 6) into the renal artery of hypertensive patients just prior to diagnostic renal angiography. In group I, stepwise increasing doses of doxazosin were associated with increases in renal perfusion and, at doses above 1 microgram kg-1 min-1, also with a fall in blood pressure. Compared with observations in control subjects, doxazosin enhanced renal renin release at rest but did not modify the renin response to isometric exercise in group II. alpha 1-Adrenoceptors are involved in causing renal vasoconstriction and inhibition of renin secretion. However, the latter is only of importance in resting subjects.