Regulation of reproductive seasonality in the red deer hind: oestradiol-dependent and -independent influences on the patterns of LH concentrations.
The control of reproductive seasonality was studied in farmed adult red deer hinds that had been either ovariectomized or ovariectomized and oestradiol-treated (s.c. implants). The breeding season, delineated by progesterone secretion in intact hind herdmates, was characterized by high (mean 0.6, range 0.1-2.5 ng ml-1 plasma) LH concentrations in ovariectomized oestradiol-treated hinds. In contrast, during the non-breeding season plasma LH concentrations in these animals were significantly lower (mean 0.1, range 0-0.9 ng ml-1 plasma). LH secretion in ovariectomized untreated hinds also displayed a marked seasonal pattern, approximately the inverse of daily photoperiod (that is, a winter peak and summer trough). The pituitary LH response to 10 micrograms exogenous GnRH was also maximal during the breeding season in ovariectomized (mean 7.4, range 1.2-14.6 ng ml-1) and ovariectomized, oestradiol-treated (mean 16.4, range 1.4-32.3 ng ml-1) hinds. These results indicate that LH secretion in the hind is regulated by both steroid-dependent and -independent mechanisms.
Meikle
L M
LM
AgResearch, Invermay Agricultural Centre, Private Bag, Mosgiel, New Zealand.
Fisher
M W
MW
D000818:Animals; D003670:Deer / Q000097:blood / Q000502:physiology*; D004958:Estradiol / Q000097:blood / Q000494:pharmacology / Q000502:physiology*; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism*; D010052:Ovariectomy; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism; D012098:Reproduction / Q000502:physiology*; D012621:Seasons
D007987:Gonadotropin-Releasing Hormone; D004958:Estradiol; D007986:Luteinizing Hormone