Human pancreatic growth hormone (GH)-releasing hormone stimulates GH synthesis and release in infant rats. An in vivo study.
Administration of human pancreatic GH-releasing factor 1-40 (hpGRF-40) at doses of 1, 10, 20, 100, and 500 ng/100 g BW sc induced in 10-day-old rats a clear-cut rise in plasma GH 15-min post-injection, although the effect was not dose-related and peak GH levels were already present after the lowest GRF dose. In 25-day-old rats, hpGRF induced only a slight rise in plasma GH at the dose of 500 ng/100 g BW sc, whereas it was completely ineffective at the lower doses. In 5-day-old rats, hpGRF (20 ng/100 g BW sc twice daily), administered for 5 days, induced a marked rise in pituitary GH content and plasma GH levels determined 14 h after the last hpGRF injection. In these rats, at the end of treatment, a challenge hpGRF dose (20 ng/100 g BW) induced a rise in plasma GH significantly higher than in infant rats receiving only the challenge hpGRF dose. These data show that: 1) pituitary responsiveness to hpGRF is strikingly higher in infant than in post-weaning rats; 2) in infant rats, subacute administration of hpGRF stimulates GH synthesis and release.
D000818:Animals; D000831:Animals, Newborn / Q000097:blood*; D005260:Female; D013006:Growth Hormone / Q000097:blood*; D013007:Growth Hormone-Releasing Hormone / Q000494:pharmacology*; D006801:Humans; D008297:Male; D010446:Peptide Fragments / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012737:Sex Factors; D013997:Time Factors; D014886:Weaning
D010446:Peptide Fragments; C036893:somatotropin releasing factor 40; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone