Comparison of the delayed actions of growth hormone and somatomedin on adipose tissue metabolism.
Although acute insulin-like effects of growth hormone (GH) on adipose tissue are readily demonstrable in vitro, it has not been possible to reproduce in vitro the delayed (3 h) inhibition of glucose utilization seen after the administration of GH in vivo. To examine the possibility that somatomedin (Sm), the postulated mediator of GH action, might, like GH, have biphasic effects on adipose tissue metabolism and mediate the delayed inhibition of glucose utilization, Sm was prepared by gel filtration from an acid-ethanol extract of normal rat plasma. The partially purified material increased 35SO4 incorporation into costal cartilage of hypophysectomized rats and produced in adipose tissue an acute stimulation of glucose oxidation that was not suppressed by insulin anti-serum. Unlike GH, whose insulin-like effects disappear in 3--4 hours, Sm-stimulated glucose oxidation remained linear for the entire 4 hour incubation period. Although acute stimulation of tissues with GH rendered them refractory to renewed insulin-like stimulation by GH, no such refractoriness to the action of Sm was seen. Furthermore, acute stimulation with Sm failed to render tissues refractory either to itself or to GH. Finally, Sm failed to reproduce the delayed lipolytic effects produced by GH in conjunction with glucocorticoids. These results make it highly unlikely that Sm alone accounts for the delayed metabolic effects of GH.
D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002356:Cartilage / Q000187:drug effects; D004822:Epididymis; D005947:Glucose / Q000378:metabolism; D013006:Growth Hormone / Q000494:pharmacology*; D050356:Lipid Metabolism; D008297:Male; D010084:Oxidation-Reduction; D010902:Pituitary Gland / Q000502:physiology; D051381:Rats; D013002:Somatomedins / Q000494:pharmacology*
D013002:Somatomedins; D013006:Growth Hormone; D005947:Glucose