Abnormal Biochemistry of Subcellular Membranes Isolated from Nonvascular Smooth Muscles of Spontaneously Hypertensive Rats

Microsomal fractions enriched in plasma membranes and endoplasmic reticulum were isolated from stomach fundus and vas deferens from age-matched Okamoto spontaneously hypertensive (SHR) rats and corresponding Kyoto-Wistar normotensive rats (KWR). Alterations of several enzyme activities and Ca2+ accumulation of the isolated microsomal fraction from these nonvascular smooth muscles provide direct evidence of abnormal smooth muscle membrane biochemistry in SHR. Decreased Ca2+ accumulation in the presence of but not in the absence of adenosine triphosphate by the microsomal fractions of both fundus and vas deferens from SHR is consistent with previous findings using plasma membranes from vascular smooth muscles from SHR and cannot be explained in terms of adaptation induced by elevation of blood pressure in SHR. Defective Ca2+ handling now observed in both vascular and nonvascular smooth muscles from hypertensive animals not only provides a cellular basis for the altered reactivity and contractility of smooth muscles observed in SHR, but also supports the hypothesis that spontaneous hypertension is associated with a generalized widespread alteration in smooth muscle membrane fraction.