Abstract
Urine flow and composition were determined in normally hydrated, waterloaded and hypotonic saline infused hens under various ambient temperatures (Ta). At Ta 29 and 32.degree. C normal urine flow was reduced and osmolality increased; at Ta 0 and -5.degree. C urine flow increased and osmolality decreased. In hydrated hens at Ta 32.degree. C antidiuresis occurred within 10 min and persisted for 2 h without any significant change in rectal temperature (Tr). At Ta 40.degree. C there was no antidiuresis but a tendency for urine flow to increase; Tr also rose. The antidiuresis shown by water-restricted hens at Ta 20.degree. C was abolished at Ta 40.degree. C. An antidiuresis, similar to that seen at Ta 32.degree. C, could be produced at Ta 20.degree. C by moderate hemorrhage, exposure to IR heating or by vasopressin or vasotocin. Adrenaline [epinephrine] and noradrenaline [norepinephrine] provoked a diuresis. Hypothalamic heating failed to elicit an antidiuresis but hypothalamic cooling increased urine flow at Ta 20.degree. C and abolished the antidiuretic response at Ta 32.degree. C. The antidiuresis seen at warm ambient temperatures is probably caused by the release of antidiuretic hormone, possibly as a response to a rise in skin temperature.