Regulation of insulin-like growth factor II receptors by growth hormone and insulin in rat adipocytes.
The acute and long-term effects of growth hormone (GH) on the binding of insulin-like growth factor II (IGF-II) were evaluated in adipose cells from hypophysectomized rats given replacement therapy with thyroxine and hydrocortisone and in cells from their sham-operated littermates. After the cells were incubated with insulin and/or GH, the recycling of IGF-II receptors was metabolically inhibited by treating the cells with KCN. IGF-II binding was 100 +/- 20% higher in cells from GH-deficient animals when compared with sham-operated controls. These GH-deficient cells also showed an increased sensitivity for insulin as compared with control cells (the EC50 for insulin was 0.06 ng/ml in GH-deficient cells and 0.3 ng/ml in control cells). However, the maximal incremental effect of insulin on IGF-II binding was reduced approximately 27% by hypophysectomy. GH added to the incubation medium increased the number of IGF-II binding sites by 100 +/- 18% in cells from hypophysectomized animals. This increase was rapidly induced (t1/2, approximately 10 min), but the time course was slower than that for the stimulatory effect of insulin. Half-maximal effect of GH on IGF-II binding was obtained at approximately equal to 10 ng/ml. Thus, GH added in vitro exerted a rapid insulin-like effect on the number of IGF-II receptors. GH also appears to play a regulating role for maintaining the cellular number of IGF-II receptors and, in addition, modulates the stimulatory effect of insulin on IGF-II binding.
D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D013006:Growth Hormone / Q000494:pharmacology*; D006854:Hydrocortisone / Q000494:pharmacology; D007016:Hypophysectomy; D007328:Insulin / Q000494:pharmacology*; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011972:Receptor, Insulin / Q000187:drug effects / Q000378:metabolism*; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000378:metabolism*; D013974:Thyroxine / Q000494:pharmacology
D007328:Insulin; D017451:Receptors, Somatomedin; D013002:Somatomedins; D007335:Insulin-Like Growth Factor II; D013006:Growth Hormone; D011972:Receptor, Insulin; D013974:Thyroxine; D006854:Hydrocortisone