Abstract
The pituitary glands of mature male rats were removed and either exposed to ice cold buffer solution or kept at room temperature for 5–15 min, and then incubated at 37°C. The levels of GH, LH and prolactin, released into the medium, were measured by specific radioimmunoassays. The pre-cooling of the pituitary glands augmented the basal release of these pituitary hormones during the first 1-hour period of incubation. Purified pig hypothalamic fractions were tested for GH-releasing hormone (GH-RH) and prolactin release-inhibiting factor (PIF) activity under the cooling or non-cooling conditions. PIF activity was demonstrated only when pituitaries were not exposed to cooling. GH-RH activity was not demonstrated under either condition in the fraction containing PIF.