Section 41
Chapter 40,459

Insulin action in isolated fat cells. II. Effects of divalent cations on stimulation by insulin of protein synthesis, on inhibition of lipolysis by insulin, and on the binding of 125I-labelled insulin to isolated fat cells

Akhtar, R.A.; Perry, M.C.

Biochimica et Biophysica Acta 585(1): 117-127


ISSN/ISBN: 0006-3002
PMID: 444585
DOI: 10.1016/0304-4165(79)90331-3
Accession: 040458587

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The effects of ommission of Ca2+ and Mg2+ from the incubation medium on three aspects of insulin action in isolated fat cells have been investigated. In the (Ca2+ + Mg2+)-free incubation medium incorporation of L-[14C]leucine into fat cell protein was reduced in the absence of insulin. Insulin stimulated L-[14C]leucine incorporation only in the presence of added CaCl2 or MgCl2. Incubation of the cells in the (Ca2+ + Mg2+)-free medium reduced but did not abolish the ability of adrenaline to stimulate lipolysis or the ability of insulin to inhibit the adrenaline-stimulated lipolysis. Specific binding of 125I-labelled insulin to the fat cells was reduced in the absence of Ca2+ and Mg2+ but was not abolished, even in the presence of EDTA. Ca2+ was routinely the most effective divalent cation in supporting these aspects of insulin action, but similar responses were obtained with Mg2+, Sr2+ and Ba2+. Since insulin still binds to the cells under conditions in which some of the cellular effects of the hormone are abolished, it is suggested that divalent cations may have a role, either direct or indirect, in the processes linking the insulin-insulin receptor complex to certain effector systems in the cells. It is tentatively suggested that this action occurs at the level of the fat cell plasma membrane.

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