Ca**. Mg4"4" - ATPase activity in insulin-dependent and non-insulin dependent diabetic Nigerians

Abstract

A study of Ca++, Mg++ - ATPase activity was carried out in normal (HHm) and diabetic Nigerians of both sexes with insulin-dependent diabetes mellitus (IDDM) and noninsulin dependent diabetes mellitus (NIDDM). The results showed that protein concentration of erythrocyte ghost membranes of healthy humans (HHm) was the highest NIDnCM0mPrd pr°tein concentrations of IDDM and innM ITT ,e protein concentration was lowest in HHm ^H nnu ™ NIDDM Was between th°se HHm and IDDM. The basal activities of erythrocyte Ca~ wJr^T hT ?DM 3,1(1 NIDDM were determined and were found to be significantly lower than that of HHm The addition of calmodulin (CaM) 2 ng/ml stimulated the ^,of calcium pump in all the groups (IDDM, NIDDM and HHm). The effects of calcium (Ca~) and adenosine triphosphate (ATP) on the activity of the pump from each group were determined. Enzyme kinetics (Km and V^) revealed that the activity of Ca~, Mg~ ATPase was initiated by ATP in the presence of Ca~ in a dose-dependent manner. Calmodulin also enhanced the activity of the enzyme in the presence of Ca~ in all the groups, though activities in IDDM and NIDDM were significantly lower than in HHm. There was no significant difference in the activities between IDDM and NIDDM. These results suggest a defective calcium translocating mechanism in diabetic Nigerians