Effects of GRF with or without a SRIF antiserum on GH, IGF-1, thyroxin, cholecystokinin, gastrin and metabolite concentrations in growing rats.

This study was undertaken to examine the effects of increasing doses of rat somatocrinin (GRF) with or without a somatostatin antiserum (SS-ab) on serum hormone and metabolic concentrations, as well as serum and duodenal cholecystokinin (CCK) and antral gastrin concentrations. 24-day-old male Sprague-Dawley rats were injected twice daily s.c. (10:00 and 16:30) for 14 consecutive days with either saline or rat GRF (1-43) NH2 (4 and 20 micrograms/kg) in gelatin. Three other groups of animals received the same treatment in association with the SS-ab given i.p. every other day making up the 6 groups of 12 animals in a 2 x 3 factorial design experiment. GRF treatment increased circulating growth hormone (GH) concentrations in a dose-dependent manner, alone or in combination with the SS-ab; the SS-ab treatment alone or combined with GRF also increased GH concentrations. Total hypophyseal GH content was increased (P < 0.05) by the GRF treatment alone. Serum levels of IGF-1, acetoacetate, alpha 2 globulin and antral gastrin were all increased by the GRF treatment with plateaus observed for antral gastrin and serum IGF-1 levels at the intermediary dose of GRF. Serum concentrations of T4 were reduced at the 4 micrograms/kg dose of GRF. Serum concentrations of CCK were increased by the SS-ab treatment alone, an effect reversed by increasing doses of GRF. Rat GRF produced a dose-dependent increase and decrease of alpha 2 globulin and albumin, respectively. These data indicate that GRF, probably via its effect on GH release, influences gastrointestinal hormone levels which are implicated in gastrointestinal organ growth and digestive processes.