Refractoriness to the insulin-like effects of growth hormone depends upon calcium

Endocrinology
Y Schwartz, H M Goodman

Abstract

GH produces an acute but transient insulin-like response in adipocytes that have been deprived of GH for at least 3 h. The insulin-like response is followed by a period of refractoriness during which a second insulin-like response to GH cannot be elicited. These studies were undertaken to evaluate the role of calcium in the insulin-like response and refractoriness. Methionyl human GH (hGH) (100 ng/ml) increased the incorporation of D-[3-3H] glucose into lipid by 50-100% in fat cells that preincubated for 3 h without hormone and usually by less than 10% in fat cells that were made refractory by exposure to 100 ng/ml of hGH in the first hour of incubation. Insulin (100 microU/ml) increased lipogenesis by 3-5-fold whether fat cells were sensitive or refractory to GH. To determine whether calcium plays a role in either the insulin-like response to GH or the refractory phenomenon, we examined the effects of trifluoroperazine (20 or 50 microM) and calmidazolium (1.0 microM) which block calmodulin, as well as verapamil (30 microM), which blocks calcium channels. These agents did not interfere with stimulation of incorporation of D-[3-3H]glucose into lipid by GH (100 ng/ml) or insulin (100 microU/ml) but restored sensitivity to the ins...Continue Reading

Citations

Aug 10, 2001·Cellular Signalling·T ZhuP E Lobie
Aug 1, 1991·Proceedings of the National Academy of Sciences of the United States of America·Y SchwartzH Yamaguchi
Jul 18, 2002·Obesity Reviews : an Official Journal of the International Association for the Study of Obesity·S Y Nam, P E Lobie
Feb 13, 2001·Endocrine Reviews·D Le RoithA Butler

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