Pituitary and Plasma Growth Hormone-Like Activity after Administration of Highly Purified Pig Growth Hormone-Releasing Factor ∗

Summary

The effect of administration of highly purified pig GH-releasing factor (GRF) on the depletion of pituitary growth hormone (GH) content in recipient rats and levels of plasma GH-like activity were investigated using the tibia test method. It was demonstrated that GRF induced a significant increase in plasma GH-like activity which was accompanied by a simultaneous decrease in pituitary GH content. The levels of plasma GH-like activity in recipient rats treated with saline were not detectable (less than 1.25 μg/ml). These results seem to confirm that the “depletion” of pituitary GH content in rats caused by GRF indicates the “release” of GH.