Effect of hypophysectomy on hypothalamic growth hormone-releasing factor content and release in the rat.
The possible regulation of hypothalamic GH-releasing factor (GRF) by GH was studied in untreated and GH-treated hypophysectomized rats by measurement of rat hypothalamic GRF content and release in vitro with a specific GRF RIA. Two weeks after hypophysectomy, animals not receiving hormone replacement showed a marked reduction in hypothalamic GRF content (to 28% of sham-operated control values; P less than 0.001). Replacement therapy with T4, cortisone, and testosterone for 9 days did not correct the decrease in hypothalamic GRF content in hypophysectomized rats, though the addition of GH therapy partially restored GRF levels (to 55% of control values; P less than 0.001). GRF release from incubated mediobasal hypothalamic fragments of hypophysectomized rats was decreased both basally and in response to 30 mM K+. This defect was completely corrected by prior GH treatment. The results suggest an impairment of GRF synthesis and release in the presence of GH deficiency.
D000818:Animals; D003348:Cortisone / Q000494:pharmacology; D013006:Growth Hormone / Q000494:pharmacology; D013007:Growth Hormone-Releasing Hormone / Q000378:metabolism*; D007016:Hypophysectomy; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013739:Testosterone / Q000494:pharmacology; D013974:Thyroxine / Q000494:pharmacology
D013739:Testosterone; D013006:Growth Hormone; D013007:Growth Hormone-Releasing Hormone; D013974:Thyroxine; D003348:Cortisone