Plasma LH levels after ovariectomy, corpus luteum removal and estradiol administration in cattle.

Abstract

Plasma LH was measured in heifers after estrogen injection, sham operation, ovariectomy, corpus luteum (CL) removal, and following combinations of these treatments. All treatments were initiated on days 13–15 of the estrous cycle. No changes in plasma LH levels were observed following sham operations or estrogen injections into intact animals. LH levels rose slowly and then fell during the first 30 hr following either ovariectomy or corpus luteum removal. The mean LH level for the 30 hr following CL removal was significantly higher than in control animals (p < 0.05), but significantly lower than in the ovariectomized animals (p < 0.01). Estradiol injections given at the time of ovariectomy or CL removal had no significant effect on mean LH level during the first 30 hr. When estradiol benzoate injections were given at the time of either CL removal or ovariectomy and again 12 hr later, they were followed by sharp LH peaks 42.0 ± 3.7 hr after ovariectomy and 39.0 ± 5.6 hr after CL removal. When no estrogen i...