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American Journal of Clinical Nutrition, Vol 58, 209-214, Copyright © 1993 by The American Society for Clinical Nutrition, Inc
ORIGINAL RESEARCH COMMUNICATIONS |
FK Ghishan
Department of Pediatric Gastroenterology/Nutrition, Vanderbilt University Medical Center, Nashville, TN 37232-2576.
The current study was designed to examine calcium transport across the basolateral membrane of the enterocyte of control and diabetic rats. The slope of initial rate of ATP-dependent calcium uptake was significantly greater in controls than in diabetic rats (P < 0.001). Kinetic analysis of ATP-dependent calcium uptake showed a maximum velocity (Vmax) of 0.19 +/- 0.02 and 0.37 +/- 0.01 mumol.g protein-1.-s- 1 in diabetic and control rats, respectively (P < 0.01). Km values were similar. Insulin therapy and calmodulin added to freeze-thawed basolateral membranes vesicles stimulated Vmax of ATP-dependent calcium uptake in diabetic membranes to values close to those of controls without a change in Km values. In contrast, the C(++)-Na+ exchange process was similar in both control and diabetic rats. These results suggest that the ATP-dependent calcium uptake process is decreased in diabetic animals. This decrease is stimulated by calmodulin or insulin therapy, implying a causal relationship between insulin deficiency and calmodulin activity in diabetes.
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