Hemodynamic effects on aortic enzyme activities in spontaneously hypertensive rats.

Spontaneously hypertensive rats (SHRSP and SHR) and normotensive WKR were treated with hypotensive drugs, and arterial and venous enzyme activities were compared between treated and nontreated hypertensive groups. With the 4 month experiment, cholesterol esterase activity in the aorta from hypertensive SHRSP and SHR was significantly lower than that in the respective treated groups, whereas venous activity did not differ. By contrast, aortic NAGA activity was significantly higher in the hypertensive groups without any changes in venous activity. Acid phosphatase activity was unaltered. No effects of treatment were observed in the normotensive WKR. Accompanying a decrease in aortic cholesterol esterase, there was a marked increase in aortic cholesteryl esters accompanying hypertension. Aortic phosphodiesterase activity was significantly elevated in the hypertensive SHRSP and SHR compared with the respective treated groups. These results suggest that hypertension of long duration specifically decreased aortic cholesterol esterase activity with a consequent accumulation of cholesteryl esters in the aorta, and that this hemodynamic effect seemed to be partly mediated by cyclic AMP with an effect on the lysosomal membrane. These results could provide the biochemical bases for the relationship between hypertension and atherosclerosis.