Pituitary and hypothalamic action of progestagens in castrated female rats.
Different doses of progesterone, D-norgestrel and delta 15-D-norgestrel were injected subcutaneously for 7 days to female rats castrated 7 days prior to the experiments. One day after the last steroid injection a i.p. LH-RH test was performed, blood samples were collected by heart puncture and serum levels of r-LH and r-FSH were estimated by radioimmunoassay. LH-RH serum levels were determined in progestagen treated control groups by an anterior pituitary cell culture bioassay. Dose dependent inhibitory effects of steroids on LH-RH stimulated gonadotropin release were observed and a dissociation of r-LH and r-FSH serum levels was found. The modulatory influence of progestagens used in this study on LH-RH provoked gonadotropin release correlated with their biological efficiency evaluated in the Clauberg test. Progesterone, D-norgestrel and delta 15-D-norgestrel treatment had no significant effects on basal r-LH levels, but LH-RH provoked r-LH levels were higher than in the control animals. Progesterone and D-norgestrel suppressed basal as LH-RH stimulated r-FSH levels, whereas delta 15-D-norgestrel showed a complex influence on r-FSH secretion. A progestagen stimulated rise of LH-RH serum levels was found and indicated an additional effect of these hormones at the hypothalamic level. These data suggest the action of progestagens at various levels of the hypothalamus-pituitary axis.
D000818:Animals; D002369:Castration; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D007987:Gonadotropin-Releasing Hormone / Q000097:blood / Q000494:pharmacology; D006065:Gonadotropins, Pituitary / Q000378:metabolism*; D007028:Hypothalamic Hormones / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000378:metabolism; D009644:Norgestrel / Q000494:pharmacology*; D011374:Progesterone / Q000494:pharmacology / Q000502:physiology*; D051381:Rats
D006065:Gonadotropins, Pituitary; D007028:Hypothalamic Hormones; D007987:Gonadotropin-Releasing Hormone; D009644:Norgestrel; D011374:Progesterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone