Compared myocardial and vascular effects of captopril and dihydralazine during hypertension development in spontaneously hypertensive rats.

1 When administered to young spontaneously hypertensive rats (SHRs), dihydralazine (25 mg kg−1, daily) and captopril (100 mg kg−1, daily) prevent with the same efficacy genetic hypertension development (GHD). 2 Dihydralazine treatment increased vascular mesenteric compliance, as shown by a significant decrease in the stiffness of the vessels (-27%), and induced slight reductions in contractility (-12%) and in wall to lumen (W/L) ratio (-15%). After treatment withdrawal, all these parameters returned to control values within 7 weeks, as did blood pressure. 3 Captopril treatment also strongly increased the mesenteric vessels compliance, vessel stiffness being decreased by 16%, and reduced their contractility (-15%) and their W/L ratio (—30%). These effects as well as those exerted on blood pressure persisted up to 7 weeks after treatment ceased although there was a slight trend to a progressive reduction in the intensity of both phenomena. 4 These experiments show that captopril but not dihydralazine has a long-lasting effect in opposing the functional and morphological vascular alterations occurring during GHD in SHRs and this phenomenon probably contributes to a large extent to the sustained preventive effects of the drug against GHD.