AJP - Endocrinology and Metabolism, Vol 255, Issue 5 E723-E729, Copyright © 1988 by American Physiological Society
Rapid and transitory stimulation of 3-O-methylglucose transport by growth hormone
C. Carter-Su, F. W. Rozsa, X. Wang and J. R. Stubbart
Department of Physiology, University of Michigan Medical School, Ann Arbor 48109-0622.
The regulation of hexose transport by growth hormone (GH) was investigated
using isolated rat adipocytes. GH caused a rapid (less than 3 min) rise in
rates of 3-O-methylglucose transport that reached a maximum of two to six
times the basal rates in 10-30 min. The stimulation of transport was
transitory, and rates of transport started to decline 15-30 min after GH
was added. Transport stimulation required a period of preincubation; no
stimulation was observed in freshly isolated cells. GH stimulated hexose
transport between 100 and 5,000 ng/ml, with a 50% effective dose between
200 and 300 ng/ml. Depletion of cellular ATP by 2,4-dinitrophenol blocked
the ability of GH to stimulate transport but not the decline of transport
rates following stimulation by GH. In contrast, an inhibitor of RNA
synthesis, actinomycin D, had no effect on either the initial stimulation
by GH or the initial subsequent decline of transport when added
simultaneously or 15 min prior to GH. Actinomycin D did, however, cause a
second rise in hexose transport at approximately 120 min that was blocked
by 2,4-dinitrophenol. These results suggest that changes in glucose
transport contribute to the effects of GH on carbohydrate and lipid
metabolism in adipose tissue. These changes are rapid, of substantial
magnitude, and of a complex nature, suggesting that regulation of glucose
transport by GH most likely involves multiple mechanisms.
