The effect of streptozocin (STZ)-induced diabetes on the plasma membrane calcium uptake of rat liver was investigated. Plasma membrane preparations from diabetic rats showed a 2–3-fold increase in calcium uptake activity over controls 3–4 wk after the initial injections. Such an increase can be either reversed or blocked by treating the diabetic rats with exogenous insulin or administering nicotinamide 15 min before and 3 h after the STZ injection, respectively. The activity of 5'-nucleotidase and the [3H]ouabain binding to the plasma membranes were similar in samples from both the control and diabetic rats. These findings made it unlikely that preferential enrichment of plasma membranes or increased proportion of inside-out vesicles was the cause of the enhanced calcium uptake activity in membranes from diabetic animals. In addition, the effect of diabetes on the calcium uptake activity did not diminish even when the assay was performed in the presence of 2.5 μM ruthenium red, an inhibitor of calcium uptake by mitochondria, or when oxalate was omitted from the assay, suggesting that the effect was specifically on the plasma membrane pump. The enhanced calcium uptake activity was a result of an increase in the Vmax (58.8 versus 113.1 pmol calcium/mg protein/min for control and diabetic rats, respectively). No significant change in Km for calcium was detected.
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Original Contributions|
November 01 1984
The Effect of Streptozocin-induced Diabetes on the Plasma Membrane Calcium Uptake Activity of Rat Liver
Kwok-Ming Chan;
Kwok-Ming Chan
Division of Laboratory Medicine, Departments of Pathology and Medicine, Washington University School of Medicine
St. Louis, Missouri 63110
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Kurt D Junger
Kurt D Junger
Division of Laboratory Medicine, Departments of Pathology and Medicine, Washington University School of Medicine
St. Louis, Missouri 63110
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Address reprint requests to Kwok-Ming Chan, Ph.D., at the above address.
Diabetes 1984;33(11):1072–1077
Article history
Received:
September 23 1983
Revision Received:
May 08 1984
Accepted:
May 08 1984
PubMed:
6209183
Citation
Kwok-Ming Chan, Kurt D Junger; The Effect of Streptozocin-induced Diabetes on the Plasma Membrane Calcium Uptake Activity of Rat Liver. Diabetes 1 November 1984; 33 (11): 1072–1077. https://doi.org/10.2337/diab.33.11.1072
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