Somatomedin-C stimulates glycogen synthesis in fetal rat hepatocytes.
The effects of somatomedin-C/insulin-like growth factor I (Sm-C) on glycogen metabolism in cultured hepatocytes from 20-day-old rat fetuses have been examined and compared with the effects of insulin. Sm-C (25-375 ng/ml; 3.25-50 nM) stimulated dose-dependent increases in [14C]glucose incorporation into glycogen (14.4-72.9%; P less than 0.001) and total cell glycogen content (10.6-34.3%; P less than 0.01). Maximal stimulation of glycogen synthesis by Sm-C occurred at 2-4 h of incubation. Insulin (10 nM to 10 microM) also stimulated [14C]glucose incorporation but its potency was only 1/20th that of Sm-C. The time course of stimulation of glucose incorporation by insulin was identical to that of Sm-C, the dose-response curves of the two hormones were parallel, and the maximal effects of insulin were not enhanced by simultaneous exposure of cells to Sm-C. These findings suggest that Sm-C and insulin stimulate glycogenesis in fetal liver through similar or identical mechanisms. Since the potency of Sm-C was 20 times greater than that of insulin, the glycogenic action of insulin in fetal liver may be mediated through binding to a hepatic receptor which also binds Sm-C. In addition to having mitogenic effects on fetal tissues, Sm-C may have direct anabolic effects on fetal carbohydrate metabolism.
D000818:Animals; D002250:Carbon Radioisotopes; D004305:Dose-Response Relationship, Drug; D005260:Female; D005333:Fetus / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D066298:In Vitro Techniques; D007334:Insulin-Like Growth Factor I; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008112:Liver Glycogen / Q000096:biosynthesis*; D011247:Pregnancy; D051381:Rats; D013002:Somatomedins / Q000494:pharmacology*
D002250:Carbon Radioisotopes; D008112:Liver Glycogen; D013002:Somatomedins; D007334:Insulin-Like Growth Factor I; D005947:Glucose