Stimulation of corticosterone release in the fowl by recombinant DNA-derived chicken growth hormone

The effects of recombinant DNA-derived chicken growth hormone (rcGH) on plasma corticosterone in young broiler cockerels were investigated. A single injection of 200 micrograms/kg rcGH significantly increased plasma corticosterone concentrations 2 hr (but not 20 or 40 min) after treatment. Administration of 10 or 100 micrograms/kg rcGH also significantly increased plasma corticosterone levels after 2 hr, with the higher dose eliciting greater responses. Chronic treatment with seven daily injections of the same doses of rcGH gave similar increases in plasma concentrations of corticosterone. No obvious difference in magnitude of plasma corticosterone was observed between acute and chronic exposure to rcGH. In a further experiment in which serial blood sampling was performed after a single injection or five daily injections of vehicle or 200 micrograms/kg rcGH, there were significant increases in plasma corticosterone concentrations 40 min after acute rcGH treatment and 40 and 80 min after chronic treatment when compared with plasma corticosterone concentrations of vehicle-injected controls. However, the increases could have incorporated a stress response due to repeated sampling because the control birds also showed elevated plasma corticosterone concentrations. The corticosterone response did not diminish with repeated GH challenge. These results suggest that GH may play a role in the acute regulation of corticosterone secretion in intact chickens.