Stimulation of growth hormone secretion by human pancreatic growth-hormone-releasing factor and thyrotrophin-releasing hormone in anaesthetized chickens.

Sodium pentobarbitone anaesthesia depressed the concentration of growth hormone (GH) in the plasma of young (6 weeks of age) and old (22-30 weeks of age) domestic fowl. In both cases the concentration was reduced (P less than 0.05) within 10 min and had declined (P less than 0.001) to stable low levels (less than 5 ng/ml) within 50 min. The intravenous administration of synthetic human pancreatic growth-hormone-releasing factor (hpGRF) (10 micrograms/kg) (2 X 10(-9) mol/kg) increased (P less than 0.01) the GH concentration in both the young and old birds. This effect was observed irrespective of whether the birds were conscious or anaesthetized. The magnitude of the response in conscious young birds (164 ng/ml) was, however, greater (P less than 0.01) than that in anaesthetized chicks (64 ng/ml). The response in anaesthetized adult fowl (18.8 ng/ml) was also less (P less than 0.05) than that in their conscious counterparts (42.8 ng/ml). The GH response in conscious and anaesthetized 6-week-old birds to hpGRF was greater (P less than 0.01) than that in the corresponding adult birds. Thyrotrophin-releasing hormone (TRH) (10 micrograms/kg (2.8 X 10(-8) mol/kg); iv) also provoked (P less than 0.01) GH secretion in conscious and anaesthetized young birds and in anaesthetized (but not conscious) adults. Anaesthesia blunted (P less than 0.01) the GH response to TRH in the immature cockerels, although the response was greater (P less than 0.05) than that in anesthetized adults.(ABSTRACT TRUNCATED AT 250 WORDS)