Effect of diabetes on cytosolic free Ca2+ and Na(+)-K(+)-ATPase in rat aorta

• Published in: Diabetes (New York, N.Y.) Vol. 40; no. 11; pp. 1560 - 1563
• Main Authors: Ohara, T., Sussman, K. E., Draznin, B.
• Format: Journal Article
• Language: English
• Published: American Diabetes Association 01.11.1991
• ISSN: 0012-1797; 1939-327X; 0012-1797
• DOI: 10.2337/diabetes.40.11.1560

Effect of diabetes on cytosolic free Ca2+ and Na(+)-K(+)-ATPase in rat aorta. T Ohara , K E Sussman and B Draznin Medical Research Service, Veterans Affairs Medical Center, Denver, CO 80220. Abstract We examined Na(+)-K(+)-ATPase activity and the levels of alpha I-, alpha II-, and beta-subunit mRNA and protein in aortic cells of diabetic rats. Diabetes was induced by streptozocin. Na(+)-K(+)-ATPase activity was significantly reduced on the 2nd day of diabetes (9.4 +/- 1.3 vs. 17.5 +/- 2.1 mumol NADH.mg-1 protein.h-1, P less than 0.05) and remained depressed on days 7 and 14. The levels of 5.3-kilobase (kb) mRNA band of the catalytic alpha II-subunit of Na(+)-K(+)-ATPase were also decreased on the 2nd day of diabetes, whereas the second band, 3.4 kb, was not affected. Both bands were significantly decreased on days 7 and 14. This was followed by a reduction in the levels of alpha II-protein (day 14). The levels of alpha I- and beta-subunit mRNA and alpha I- protein were not affected by diabetes. A decrease in Na(+)-K(+)-ATPase activity was accompanied by a significant (P less than 0.001) increase in the cytosolic free Ca2+ concentrations [( Ca2+]i) in diabetic aortic cells (221 +/- 18 nM on the 7th day and 242 +/- 17 nM on the 14th day vs. 153 +/- 7 nM in controls). These findings are consistent with the hypothesis that decreased Na(+)-K(+)-ATPase activity and gene expression in vascular smooth muscle cells with accompanied rises in [Ca2+]i may be an important pathogenetic factor in the development of hypertension and atherosclerosis in diabetes.