Impaired calcium metabolism associated with hypertension in Zucker obese rats.

Recent data from our laboratory indicate that reduced membrane Ca-adenosine triphosphatase (ATPase) activity in non-insulin-dependent diabetics may be responsible for increases in intracellular calcium and, consequently, for elevated vascular resistance. Since obesity is frequently associated with hypertension, even before the development of overt diabetes, we evaluated blood pressure and erythrocyte cation levels and membrane Na/K-ATPase and Ca-ATPase in Zucker obese rats and their lean controls (n = 10 per group). Intra-arterial blood pressure, determined via a femoral cannula, demonstrated elevated systolic and diastolic pressure in the obese rats (P less than .05). There were no significant differences in Na/K-ATPase between groups, but there was a decrease in Ca-ATPase (P less than .01) in the obese rats and an increase in tissue and cellular calcium content (P less than .05). These data demonstrate a specific impairment in membrane Ca-ATPase activity in obese rats they may have caused the observed increase in cellular calcium and, consequently, increased blood pressure. These phenomena may result from impaired insulin activation of membrane Ca-ATPase in these insulin-resistant animals.