title: Post-somatostatin rebound secretion of growth hormone is dependent on growth hormone-releasing factor in unrestrained female rats.
abstract: To examine the characteristics of GH secretion following the termination of the infusion of somatostatin, unrestrained adult female Wistar rats were subjected to repeated infusions of somatostatin separated by 30-min control periods. When somatostatin was infused for 150 min at a dose of 3, 30 or 300 micrograms/kg body wt per h, the magnitude of the rebound GH secretion increased in a dose-dependent manner. The infusion of somatostatin at a dose of 300 micrograms/kg body wt per h for 60, 150 or 240 min progressively augmented the size of the rebound GH secretion. When an antiserum to rat GH-releasing factor (GRF) was injected i.v. 10 min before the end of the infusion, the peak amplitude of the rebound GH secretion (300 micrograms/kg body wt, 150 min) was reduced to less than 20% of that of control rats. The rebound GH secretion (300 micrograms/kg body wt per h, 150 min) was augmented by a bolus injection of human GRF (1 microgram/kg body wt). The combined effect of the end of infusion of somatostatin and a bolus injection of GRF on the amount of GH secreted was additive. The plasma GH response to GRF was completely inhibited when human GRF (3 micrograms/kg body wt per h) and somatostatin (300 micrograms/kg body wt per h) were infused simultaneously for 150 min. The magnitude of the rebound GH secretion following the termination of the co-administration was larger than that following the somatostatin infusion alone, but this rebound was not enhanced by a bolus injection of human GRF.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Internal Medicine, Nippon Medical School, Tokyo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Sugihara
authors.forename: S
authors.initials: S
authors.lastname: Minami
authors.forename: I
authors.initials: I
authors.lastname: Wakabayashi
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D013006:Growth Hormone / Q000378:metabolism*; D013007:Growth Hormone-Releasing Hormone / Q000276:immunology / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012636:Secretory Rate / Q000187:drug effects; D013004:Somatostatin / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D013004:Somatostatin; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone