The radioactive
microsphere technique was used to study the systemic and regional haemodynamic effects of the converting
enzyme inhibitor captopril (0.1, 0.3 and 1.0 mg/kg) 10 min after
intravenous administration in conscious rabbits with bilateral
cellophane perinephritis hypertension, an experimental model of
hypertension associated with normal plasma
renin levels.
Captopril lowered arterial blood pressure as a result of a dose-dependent decrease in total peripheral resistance. The fall in blood pressure was accompanied by an increase in cardiac output after the second and third dose of
captopril; heart rate was not significantly altered.
Captopril produced a generalized peripheral vasodilatation; the changes in vascular conductance being most pronounced in the kidneys, intestines and skin which resulted in a significant increase in blood flow to these vascular beds. The effective
antihypertensive properties of
captopril in this 'low plasma
renin' model of
hypertension and the uniform increase in vascular conductances produced by
captopril, which antagonizes the generalized increase in vascular resistances that characterizes
cellophane perinephritis hypertension, may indicate the involvement of an increased activity of the renin-angiotensin system, possibly in tissues, such as the vascular wall and brain, in the maintenance of the elevated blood pressure in this hypertensive form.