AJP - Endocrinology and Metabolism, Vol 241, Issue 6 460-E464, Copyright © 1981 by American Physiological Society
Ontogeny of sex differences in LH and FSH levels 48 h after castration in the rat
J. R. Lorenzen and J. A. Ramaley
Serum gonadotropin levels were measured 12, 24, and 48 h after gonadectomy
in male and female rats (ages, 22--60 days) to assess when during
development the rate of rise of luteinizing hormone (LH) and
follicle-stimulating hormone (FSH) after castration approximates that seen
in the gonadectomized adult. In females serum LH levels 48 h after
ovariectomy were increased above sham levels only when the ovaries were
removed prior to vaginal opening. Ovariectomy on the day of vaginal opening
or at older ages resulted in no increase in LH levels by 48 h after
surgery. Serum FSH levels at 24 and 48 h after ovariectomy declined with
increasing age at the time of ovariectomy. In males serum LH levels at 48 h
after castration increased with increasing age at the time of gonadectomy.
Serum FSH levels at either 12, 24, or 48 h after orchidectomy did not
change appreciably with age at the time of surgery. It is concluded that
the acute pituitary secretion of gonadotropins after removal of testes in
the immature male resembles that seen in the mature male early in the
course of the development of sexual maturity. In contrast, the acute
pituitary secretion of gonadotropins after removal of the ovaries in the
immature female does not resemble that seen in the ovariectomized adult
until she is mature and capable of ovulating. Thus, the observed delay in
the rise of LH seen in ovariectomized adults may be a function of some
aspect of the hormonal changes associated with the estrous cycle.
