Effect of hypertension and captopril treatment on the vasopressin in the rat median eminence and posterior lobe of the hypophysis. An immunohistochemical study

Abstract

The present study analyses the effects of hypertension andlor its oral treatment with captopril (angiotensine-converting enzyme inhibitor) on the rat median eminence (ME) and the posterior lobe of the hypophysis (PL). After an immunohistochemical reaction using an antibody against arginine-vasopressin, we compared by densitometry the amount of vasopressin immunoreactive material (vasopressin-ir) of these centers in 4 groups of animals: control Wistar Kyoto rats (WKY), spontaneously hypertensive rats (SHR), WKY rats treated with captopril (WKY-T) and SHR rats also treated with the same drug (SHR-T). Captopril was administrated at a dosage of 0.1 mglml in. the drinking water from the 8th to the 15th weeks. We have found that the rats showing the lowest level of vasopressin-ir, in both ME and PL, were those from the SHR group, the concentration increasing after oral captopril treatment (SHR-T), although without reaching the values of WKY rats. Then, ACE inhibition by captopril influences vasopressin content in brain areas where the hormone is concentrated before being released, which supports the hypothesis that suggests a central modulatory effect of ACE inhibitors, contributing to their therapeutic action on hypertension.