Increase in Plasma Growth Hormone (GH)-Like Activity After Administration of Porcine GH-Releasing Hormone 1

Summary

The ability of pure growth hormone (GH)-releasing hormone (GH-RH) to deplete pituitary GH content and simultaneously to increase plasma GH-like activity was investigated in the rat using the “tibia test” method. GH-RH (350 ng) induced a significant fall in pituitary GH content which was accompanied by increased GH-like activity in plasma. GH-RH administered at two dose levels, 80 and 400 ng, induced a dose-related fall in pituitary GH. There was a concomitant rise in plasma GH-like activity of rats given the larger dose. Plasma GH-like activity in rats injected with saline was not detectable. These results indicate that the pituitary depletion of GH content in rats caused by GH-RH reflects true release of the hormone.