Takashige Saito

Growth hormone-releasing activity in the hypothalamus and plasma of rats subjected to stress.

Summary Experiments were performed in the rat to determine whether the increased secretion of growth hormone (GH) during stress involves augmentation of synthesis and/or release of hypothalamlc GH-releasing factor (GRF). Two different stimuli were used as stress: injection of formalin, which was previously shown to be ineffective in inducing GH release; and cold exposure, which evoked depletion of pituitary GH. Exposure of rats to cold (4°C) for 1 hr resulted in a significant depletion of pituitary GH, which was accompanied by disappearance of hypothalamic GRF and appearance of GRF activity in plasma. Cold exposure for 5 minutes was ineffective. Injection of 10% formalin did not induce pituitary GH depletion, or affect hypothalamic and plasma GRF activity. These results indicate that some stressful stimuli, such as cold exposure, capable of releasing GH, induce this effect via the hypothalamus; other stresses, like formalin injection, which do not release GH, exert little effect on the GH-release mechanism of the hypothalamus.

Purification of growth hormone-releasing factor from beef hypothalamus.

Summary Potent preparations of growth hormone-releasing factor (GRF) were prepared from bovine hypothalamic extracts, by the glacial acetic acid concentration procedure followed by gel filtration on Sephadex. Purified GRF is distinct from vasopressin, oxy-tocin, a-MSH and other hypothalamic-releasing factors. We are grateful to Dr. E. Müller for advice on the use of his GRF assay and to Dr. William Locke for help in preparation of the manuscript.

Physiological and Biochemical Studies on Some Highly Purified Hypothalamic Releasing Factors

Since our group has been scheduled to deliver the concluding presentation, we would like to mention topics not discussed by previous speakers. For this reason, our presentation had to be improvised in part during the preceding talks, so that it will be composed of many topics.