Abstract
The anterior pituitary functions of synthesizing and releasing growth hormone (GH) and prolactin were determined in vitro after exposing the rat to mild (6°C) or severe cold (1°C) for periods ranging from 4 hr to 7 days.
1) Mild or severe cold exposure for 12 hr depressed the GH synthesis function. Severe cold exposure for 12 hr stimulated the GH release function.
2) Mild cold exposure stimulated the prolactin synthesis function within 4 hr and severe cold exposure within 2 hr. Severe cold exposure for 12 hr stimulated the prolactin release function.
3) The effects of chronic cold exposure for 7 days were substantially the same as mentioned above.
4) Pituitary whole protein synthesis was depressed by mild or severe cold exposure within 12 hr, and the effects lasted for a 7-day exposure period. Whole protein hormone release did not change significantly.
5) The serum level of free fatty acids (FFA) was elevated by severe cold exposure within 4 hr and returned to the normal level by 7 days. Serum glucose and protein did not change throughout the cold exposure period.
The observed facts suggested that the cold stimulus acts directly on the hypothalamus through neural pathways and that the altered pituitary functions of synthesizing and releasing GH and prolactin play a role in metabolic readjustment to a cold environment.
