Circulating levels of insulin and avian pancreatic polypeptide in pigeons under different experimental conditions

Changes in circulating levels of insulin and avian pancreatic polypeptide (APP) were studied in pigeons under different experimental conditions. Anesthetized pigeons in which the pectoralis muscles were stimulated electrically for periods of 1 or 5 hr showed significant reduction in plasma insulin levels but not in APP levels. Cold exposure (-15 degrees, 90 min) of fully feathered (FF) or partially (dorsum and breast) defeathered (PD) pigeons produced no significant changes in plasma levels of insulin or APP. Heat exposure (+45 degrees, 90 min) of FF and PD pigeons caused no change in plasma levels of insulin; however, APP levels were significantly increased. In pigeons subjected to bilateral cervical vagotomy, there was no change in the level of plasma insulin but APP levels were found to be significantly increased.