Growth hormone regulates the distribution of L-type calcium channels in rat adipocyte membranes.
Earlier studies demonstrated that deprivation of growth hormone (GH) for >/=3 h decreased basal and maximally stimulated cytosolic Ca2+ in rat adipocytes and suggested that membrane Ca2+ channels might be decreased. Measurement of L-type Ca2+ channels in purified plasma membranes by immunoassay or dihydropyridine binding indicated a two- to fourfold decrease after 3 h of incubation without GH. No such decrease was seen in unfractionated adipocyte membrane preparations. The decrease in plasma membrane channel content was largely accounted for by redistribution of channels to a light microsomal membrane fraction. Immunoassay of alpha1-, alpha2/delta-, and beta-channel subunits in membrane fractions indicated that the channels redistributed as intact complexes. Addition of GH during the 1st h of incubation prevented channel redistribution, and addition of GH after 3 h restored channel distribution to the GH-replete state of freshly isolated adipocytes. The studies suggest that GH may regulate the abundance of Ca2+ channels in the adipocyte plasma membrane and thereby modulate sensitivity to signals, the expression of which is Ca2+ dependent.
Gaur
S
S
Department of Physiology, University of Massachusetts Medical School, Worcester, MA 01655, USA.
Morton
M E
ME
Frick
G P
GP
Goodman
H M
HM
D017667:Adipocytes / Q000378:metabolism*; D000273:Adipose Tissue / Q000166:cytology / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000096:biosynthesis*; D020746:Calcium Channels, L-Type; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D004095:Dihydropyridines / Q000378:metabolism; D004822:Epididymis; D013006:Growth Hormone / Q000494:pharmacology / Q000502:physiology*; D017275:Isradipine / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008861:Microsomes / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D004095:Dihydropyridines; C038806:1,4-dihydropyridine; D013006:Growth Hormone; D002118:Calcium; D017275:Isradipine