Growth hormone releasing factors in the brain and the gut: chemistry, actions, and localization.
Within the physiological range of other known releasing factors, human pancreatic tumor growth hormone releasing factor (hpGRF) is specific for GH release. Data concerning hpGRF action on cAMP and GH are consistent with the concept of cAMP acting as a second messenger for this releasing factor. hpGRF-stimulated GH release is Ca++ dependent. Exogenous hpGRF40 does not alter the interdigestive gastric motility or secretion of gastrin and motilin in dogs, while large doses of hpGRF stimulate somatostatin release into the hepatic portal blood of the rat. Significant GRF activity as determined by a rat pituitary perifusion system is confined within the median eminence and the arcuate nucleus, though detectable but insignificant GRF activity is present in other area of the hypothalamus and cortex in the rat. GRF activity is present in the ovine brain as well as in the gut. Both tissues contain large (between 4000-5000 daltons) and small (but possibly larger than 1000 daltons) m.w. GRF materials. GRF appears to be structurally different between species and more than one GRF may be present within the same species. One of the ovine brain peptides with GH-releasing activity was partially characterized as His-Ser-Asp-Gly-Ile-Phe-Thr-Asp-Ser-Tyr- Lys-Arg-Try-Asn-Lys-Glu-Met- Ala-Lys--which is similar to rat GRF and porcine VIP having His at the N-terminus. Another peptide with GRF activity which eluted earlier on reverse phase HPLC and later on cation exchange chromatography has also been obtained in a pure form.(ABSTRACT TRUNCATED AT 250 WORDS)
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D001681:Biological Assay; D001921:Brain / Q000378:metabolism*; D001923:Brain Chemistry; D002118:Calcium / Q000502:physiology; D002478:Cells, Cultured; D055598:Chemical Phenomena; D002621:Chemistry; D000242:Cyclic AMP / Q000378:metabolism; D004285:Dogs; D005755:Gastrins / Q000378:metabolism; D005769:Gastrointestinal Motility / Q000187:drug effects; D013006:Growth Hormone / Q000378:metabolism; D013007:Growth Hormone-Releasing Hormone / Q000032:analysis / Q000494:pharmacology / Q000502:physiology*; D007031:Hypothalamus / Q000502:physiology; D007413:Intestinal Mucosa / Q000378:metabolism*; D008297:Male; D009037:Motilin / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology; D010477:Perfusion; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D012756:Sheep; D014018:Tissue Distribution
D005755:Gastrins; D010446:Peptide Fragments; C036893:somatotropin releasing factor 40; D009037:Motilin; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D000242:Cyclic AMP; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine