title: Effects of part sequences of human growth hormone on in vivo hepatic glycogen metabolism in the rat.
abstract: Acute effects of two part sequences of human growth hormone on the in vivo activity levels of hepatic glycogen synthase and glycogen phosphorylase were examined. The peptide corresponding to residues 6 to 13 of the hormone (hGH 6--13) decreased the percentage of phosphorylase in the active form without affecting synthase activity. This action was indirect and dependent upon insulin. The peptide hGH 177--191 decreased the level of the active form of synthase without affecting phosphorylase activity. This effect was also observed with analogous peptides containing the sequence hGH 178--191 (i.e., hGH 172--191 and hGH 178--191), whereas the peptide hGH 179--191 was inert. The onset of these effects was rapid, and maximum changes in activity were produced in 5 min by both peptides. The effect for hGH 177--191 was short-lived, and synthase activity had returned to normal levels by 15 min, whereas the action of hGH 6--13 was of longer duration and was still quite marked at 60 min. Both peptides showed a linear dependence of response to the log dose of peptide injected over the range 0.1--250 microgram hGH 6--13 per kg body weight and 0.05--25 microgram hGH 177--191 per kg body weight. Hepatic 3',5'-cyclicadenylic acid levels were not affected by either peptide. Incorporation of glycerol carbon into liver glycogen was increased by hGH 6--13 and decreased by hGH carbon into liver glycogen was increased by hGH 6--13 and decreased by hGH 177--191. This is discussed in terms of a futile cycle between glycogen and hexose phosphate in the liver, as the basis for a control mechanism for hepatic glycogen metabolism. The present observations are consistent with other in vivo and in vitro actions of these and related peptides.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D006006:Glycogen Synthase / Q000378:metabolism; D013006:Growth Hormone / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008112:Liver Glycogen / Q000378:metabolism*; D010446:Peptide Fragments / Q000494:pharmacology; D006005:Phosphorylases / Q000378:metabolism; D051381:Rats; D013329:Structure-Activity Relationship
chemical_list: D008112:Liver Glycogen; D010446:Peptide Fragments; D013006:Growth Hormone; D000242:Cyclic AMP; D006005:Phosphorylases; D006006:Glycogen Synthase