Gd. Cartee et Ee. Bohn, GROWTH-HORMONE REDUCES GLUCOSE-TRANSPORT BUT NOT GLUT-1 OR GLUT-4 IN ADULT AND OLD RATS, American journal of physiology: endocrinology and metabolism, 31(5), 1995, pp. 902-909
The primary purpose of this study was to investigate the influence of
administration of recombinant-derived human growth hormone (rhGH) to a
dult male rats of several ages (9, 20, and 31 mo) on skeletal muscle g
lucose transport. Rats were injected with rhGH (0.7 mg/kg) or vehicle
twice daily for 10 days. The rhGH treatment led to a doubling of circu
lating insulin-like growth factor I levels at each age. Skeletal muscl
e glucose transport activity was evaluated in isolated epitrochlearis
muscle with use of 3-O-methylglucose at three insulin concentrations (
0, 100, and 20,000 mu U/ml). The results indicate that, after 10 days
of rhGH administration, 1) an similar to 20-30% reduction in basal glu
cose transport activity was evident in muscles from every age group, 2
) the ability of a submaximally effective insulin concentration (100 m
u U/ml) to increase glucose transport activity above basal values was
not significantly reduced in any age group, 3) maximal insulin stimula
ted glucose transport activity (with 20,000 mu U/ml) was significantly
reduced (similar to 40%) by rhGH treatment only in the oldest rats, a
nd 4) the alterations in glucose transport activity occurred despite n
o change in skeletal muscle GLUT-1 or GLUT-4 protein levels.