On the Negative Feedback Regulation of Gonadotropins in Castrate and Intact Cattle with Comparison of Two FSH Radioimmunoassays1

Abstract

Two homologous radioimmunoassays for bovine follicle stimulating hormone (bFSH) were utilized in comparing the differential regulation of FSH and luteinizing hormone (LH) in response to ovariectomy or administration of gonadal steroids in cattle. There appeared to be significant LH cross-reactivity in one of the bFSH systems (bFSH-HS-2-17), but not in the other (bFSH-BP3). Concentrations of FSH in plasma measured by these two systems suggested both qualitative and quantitative differences. Following ovariectomy in heifers, LH concentrations in plasma were increased by 7.5 h, while FSH (measured in the bFSH-BP3 system) was not significantly elevated until 18 h. Administration of 200 micrograms of estradiol-17 beta to ovariectomized heifers inhibited levels of FSH in plasma but large doses of testosterone (100 mg), androstenedione (400 mg) and dihydrotestosterone (800 mg) had no effect. Similarly, LH was not affected by the androgens, while estradiol induced LH surges, leading to increased mean LH concentrations. In contrast to the results in heifers, LH concentrations in plasma from steers were inhibited by administration of androgens as well as by estradiol. In steers, FSH (bFSH-BP3) was marginally inhibited by estradiol and not at all by the androgens. Differences in the secretory patterns of FSH and LH also occurred in intact heifers during the estrous cycle. The 72-h period preceding estrus (follicular phase) was characterized by rapidly declining serum progesterone concentrations, followed by concurrent increases in both LH and estradiol. The circulating levels of bFSH (BP3) tended to decline during this interval. Overall, during the estrous cycle, progesterone levels were positively correlated with bFSH-BP3 (r = .37) and negatively correlated with LH (r = -.39). The gonadotropins were not significantly related (r = -.15). These relationships are consistent with the concept that LH controls the final stages of follicular development in cattle and that FSH may exert only a permissive effect.

Changes in pulsatile secretion patterns of LH, FSH, progesterone, androstenedione and oestradiol in cows after superovulation with PMSG

“…The tendency for basal FSH increase in the control cows during and after luteolysis differs from previous studies (Butler et al, 1983;Padmanabhan et al, 1984;Schallenberger et al, 1985) which report steady or declining levels. The increased pulse frequency confirms the observations of Schallenberger et al (1985).…”

Effects of gonadotropins and insulin-like growth factors-I and -II on in vitro steroid production by bovine granulosa cells

“…contain receptors for both FSH and LH (Gutiérrez et al 1997;Ireland and Roche 1987), and in vivo studies have also shown that plasma LH concentration increases during last few days of preovulatory follicular growth in cattle (Bulter et al 1983;Kawate et al 1989). Fortune and Hilbert (1986) found that an additional interaction between theca and granulosa cells might be involved in increasing E 2 production by ovarian follicles.…”

Energy Balance and Ovarian Follicle Development Prior to the First Ovulation Postpartum in Dairy Cows Receiving Three Levels of Dietary Fat

“…Total plasma cholesterol was quantified in samples collected twice weekly during the first month PP by an enzymatic assay (Sigma Chemical Co., St. Louis, MO) with inter-and intraassay CV (n = 9) of 6.9% and 5.6%, respectively. Plasma samples from Day 1 to 14 were assayed for FSH concentrations by RIA [17,18] utilizing USDA-bovine (b) FSH-BP3 for both iodination and standards, and USDA-5-0122 antibFSH-B as the first antibody at a final dilution of 1:40 000. Inter-and intraassay CV (n = 3) were 17.3% and 7.8%, respectively.…”