Membrane Abnormalities Occur in Vascular Smooth Muscle but not in Non-vascular Smooth Muscle from Rats with Deoxycorticosterone-salt Induced Hypertension

Microsomal fractions were isolated from the smooth muscle of gastric fundus, vasa deferentia and mesenteric arteries of rats made hypertensive by deoxycorticosterone-salt treatment. Several enzymatic activities, Ca2+ binding and ATP-dependent Ca2+ accumulation of the microsomal fractions from these hypertensive rats were compared with those from the control of rats which remained normotensive under similar treatment. Altered membrane properties were observed in microsomal fractions isolated from vascular smooth muscle but not in those isolated from non-vascular smooth muscles in this form of experimental hypertension. These alterations included decreased Mg2+ ATPase activity, enhanced alkaline phosphatase activity, decreased Ca2+ binding in the absence of ATP and decreased ATP-dependent Ca2+ accumulation. This result is in contrast to our previous findings that decreased ATP-dependent Ca2+ accumulation was observed in microsomal fraction isolated from non-vascular smooth muscles of rats with genetic hypertension. The present study, together with our previous findings, support the contention that altered Ca2+ handling by vascular smooth muscle is associated with the pathogenesis of hypertension, whereas altered Ca2+ handling by non-vascular smooth muscles previously observed in spontaneous hypertension may be associated with genetic factors not related to hypertension.