Effect of antihypertensive drugs on the myocardial microvessels in rats with nitric oxide blockade

Abstract

In the present study, myocardial microvessels were investigated by stereology in rats with nitric oxide blockade and concomitant antihypertensive treatment for 40 days. The following five groups (10 rats each) were studied: control; L-NAME; L-NAME + spironolactone; L-NAME + enalapril; L-NAME + verapamil. The blood pressure (BP) increased every week in the L-NAME group; after an initial increase BP decreased in the treated groups and was not different from the control group. Compared to control animals, the myocardium had hypertrophied myocytes and capillary rarefaction; the tunica media and the tunica intima of small arteries were thickened, and an increase in collagen fibrils in L-NAME treated animals was noted. The enalapril, verapamil and spironolactone groups showed uniform myocardium, quite similar to the control group. The volume density of vessels, in comparison with the L-NAME group, was greater in the spironolactone group (57%), in the enalapril group (76%) and in the verapamil group (81%). The length density of vessels was, respectively, 56%, 50%, and 76% greater in the spironolactone, enalapril and verapamil groups than in the L-NAME group. The surface density of the vessels of the L-NAME group was, respectively, 88%, 96%, and 113% lower than in the spironolactone, enalapril and verapamil groups. These results are compatible with the occurrence of angiogenesis in the verapamil rats.