Modifications induced in the renin-angiotensin-aldosterone system of rats by alpha-blocking drugs

Summary The data reported in the present paper refer to quantitative variations of plasma renin activity and plasma aldosterone levels after administration of alpha-blocking agents, i.e. phentolamine, phenoxybenzamine and gihydroergotoxin derivatives, either to rats kept on a standard diet with water ad libitum or to rats receiving distilled water load, the latter treatment causing an increase of both plasma renin activity and plasma aldosterone levels if compared to control values. No strict correlation between (a) drug-induced modifications of plasma renin activity and plasma aldosterone levels and (b) blood pressure drop caused by the same drugs was shown to occur under either experimental condition. Infact phentolamine and dihydroergotoxin derivatives exert all a more or less marked hypotensive action, which may be associated with relatively high plasma renin activita and plasma aldosterone levels, as is the case with phentolamine and phenoxybenzamine, or with low PRA and low plasma aldosterone levels, as is the case with dihydroergotoxin derivatives.