Ovarian morphology and the concentration of steroids, and of gonadotrophins during the breeding season in ewes actively immunized against oestradiol-17 or oestrone

Publisher Website
Google Scholar
Abstract
Ewes were actively immunized against estrone-6-(O-carboxymethyl)-oxime-bovine serum albumin, 17.beta.-estradiol-6-(O-carboxymethyl)oxime-bovine serum albumin or bovine serum albumin (controls). All 4 control ewes, 1 of 5 estradiol-immunized ewes and 1 of 5 estrone-immunized ewes had regular estrous cycles. The other animals displayed estrous irregularly or remained anestrous. The plasma concentrations of lutropin and, to a lesser degree, follitropin were increased relative to those in control ewes on Days 11-12 after estrus or a similar total period after progestogen treatment in ewes not showing estrus. The ovaries were examined and jugular venous blood, ovarian venous blood and follicular fluid were collected at laparotomy on Days 9-10 of the estrous cycle. The ovaries of immunized ewes were heavier than those of control ewes. There were no CL [corpora lutea] in 5 of the immunized ewes but in the other 5 there were more CL than in the control ewes. Ovaries from 4 of 5 estrone-immunized ewes contained luteinized follicles, while ovaries from 4 of 5 estradiol-immunized ewes contained very large follicles with a degenerated granulosa and a hyperplastic theca interna. Both types of follicles produced progesterone, detectable in ovarian venous plasma, and production of other steroids, particularly androstenedione, was also increased. The steroid-binding capacity of plasma was increased in the immunized ewes. The binding capacity of follicular fluid for estradiol-17.beta. and estrone was similar to that of jugular venous plasma from the same ewes. Apparently immunization against estrogens disrupts reproductive function by interfering with the feedback mechanisms controlling gonadotropin secretion.