AJP - Endocrinology and Metabolism, Vol 247, Issue 3 297-E304, Copyright © 1984 by American Physiological Society

ARTICLES

Role of calcium ions in insulin action on hexose transport in L6 muscle cells

A. Klip, G. Li and W. J. Logan

It has been proposed that Ca2+ ions mediate the stimulation by insulin of glucose uptake in muscle (Clausen, T., Cell Calcium 1:311-325, 1980). However, absolute measurements of the concentration of cytosolic free Ca2+, [Ca2+]i, during the course of insulin action have not been made. The stimulation of hexose uptake by insulin was studied in an in vitro model system of muscle cells, the L6 cell line. The following evidence suggests that Ca2+ ions are not likely to fulfill the purported role. 1) Insulin in Ca2+-free media induced stimulation of 2-deoxy-D-glucose uptake. 2) Elevation of [Ca2+]i with the ionophore A23187 did not enhance hexose uptake. 3) Insulin action was not diminished when the hormone was added to Ca2+-depleted cells in Ca2+-free media with A23187. 4) Hexose uptake was not affected by a number of agents thought to modify [Ca2+]i including epinephrine, caffeine, 2,4-dinitrophenol, hyperosmolar mannitol, salicylate, vanadate, veratrine, and trypsin. 5) Direct determinations of [Ca2+]i by fluorescence of the novel indicator Quin-2 did not show differences between basal and insulin-stimulated cells; under identical conditions hexose uptake was stimulated by the hormone. 6) Chelation of [Ca2+]i with Quin-2 in Ca2+-free media did not affect the response to insulin. 7) Low concentrations of trypsin (7.5 micrograms/ml) elevated [Ca2+]i but did not increase the rate of hexose uptake.

This article has been cited by other articles:

				J. T. Lanner, A. Katz, P. Tavi, M. E. Sandstrom, S.-J. Zhang, C. Wretman, S. James, J. Fauconnier, J. Lannergren, J. D. Bruton, et al. The role of Ca2+ influx for insulin-mediated glucose uptake in skeletal muscle. Diabetes, July 1, 2006; 55(7): 2077 - 2083. [Abstract] [Full Text] [PDF]

				N. Wijesekara, A. Tung, F. Thong, and A. Klip Muscle cell depolarization induces a gain in surface GLUT4 via reduced endocytosis independently of AMPK Am J Physiol Endocrinol Metab, June 1, 2006; 290(6): E1276 - E1286. [Abstract] [Full Text] [PDF]

				A. J. Rose and E. A. Richter Skeletal Muscle Glucose Uptake During Exercise: How is it Regulated? Physiology, August 1, 2005; 20(4): 260 - 270. [Abstract] [Full Text] [PDF]

				B. Yu, L. A. Poirier, and L. E. Nagy Mobilization of GLUT-4 from intracellular vesicles by insulin and K+ depolarization in cultured H9c2 myotubes Am J Physiol Endocrinol Metab, August 1, 1999; 277(2): E259 - E267. [Abstract] [Full Text] [PDF]

				Z. A. Khayat, T. Tsakiridis, A. Ueyama, R. Somwar, Y. Ebina, and A. Klip Rapid stimulation of glucose transport by mitochondrial uncoupling depends in part on cytosolic Ca2+ and cPKC Am J Physiol Cell Physiol, December 1, 1998; 275(6): C1487 - C1497. [Abstract] [Full Text] [PDF]

				J. P. Whitehead, J. C. Molero, S. Clark, S. Martin, G. Meneilly, and D. E. James The Role of Ca2+ in Insulin-stimulated Glucose Transport in 3T3-L1 Cells J. Biol. Chem., July 20, 2001; 276(30): 27816 - 27824. [Abstract] [Full Text] [PDF]