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KMID : 0811719990030030357
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Korean Journal of Physiology & Pharmacology
1999 Volume.3 No. 3 p.357 ~ p.364
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Role of Ca2+ in the Stimulation of Glucose Transport by Insulin in Adipocytes
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Sung-Hoe Chang
Yeon Jin Jang/Kun-Koo Park/Ghi Su Kim/Hee Jeong Ryu/C1hun Sik Park
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Abstract
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We investigated the role of Ca2+ and protein kinases/phosphatases in the stimulatory effect of insulin on glucose transport. In isolated rat adipocytes, the simple omission of CaCl2 from the incubation medium significantly reduced, but did not abolish, insulin-stimulated 2-deoxy glucose (2-DG) uptake. Pre-loading adipocytes with intracellular Ca2+ chelator, 5,5'-dimethyl bis (o-aminophenoxy)ethane-N,N,N'N' tetraacetic acetoxymethyl ester (5,5'-dimethyl BAPTA/AM) completely blocked the stimulation. Insulin raised intracellular Ca2+ concentration ([Ca2+]i) about 1.7 times the basal level of 72±5 nM, and 5,5'-dimethyl BAPTA/AM kept it constant at the basal level. This correlation between insulin-induced increases in 2-DG uptake and [Ca2+]i indicates that the elevation of [Ca2+]i may be prerequisite for the stimulation of glucose transport. Studies with inhibitors (ML-9, KN-62, cyclosporin A) of Ca2+?calmodulin dependent protein kinases/phosphatases also indicate an involvement of intracellular Ca2+. Additional studies with okadaic acid and calyculin A, protein phosphatase-1 (PP-1) and 2A (PP-2A) inhibitors, indicate an involvement of PP-1 in insulin action on 2-DG uptake. These results indicate an involvement of Ca2+?dependent signaling pathway in insulin action on glucose transport.
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KEYWORD
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Insulin, Ca2, , PP-1, 2-DG uptake, Adipocyte, 5, 5'-dimethyl BAPTA/AM,
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