Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: June 10, 1996
Publication Date: N/A
Quantities of pituitary BP's change throughout the estrous cycle in the bovine. Therefore, the objective of this experiment was to examine the influence of estradiol on pituitary BP's and concentrations of IGF-I and BP's in serum of the ovine. Amounts of messenger (m) RNA in the anterior pituitary gland for BP-2 and the gonadotropins were also determined. Chronically ovariectomized ewes received a single Silastic implant (d 1) containing estradiol (E; n=6) or no implant (C; n=4). On d 80, pituitary glands were removed and stored at -70 C. Serum concentrations (ng/ml) of IGF-I tended (p<.1) to be greater in E than C ewes (145 +/- 15 vs 106 +/- 16). Ligand blot analysis identified BP-2 (34 kDa), -3 (40 and 44 kDa), and -4 (24 and 28 kDa) in serum. In the pituitary, BP-2 (32 kDa), -3 (36 kDa and 40 kDa) and -5 (29 kDa) were detected. Relative abundance (arbitrary units) of BP-3 in serum was greater (p<.01) in E than C ewes (4.3 +/- .4 vs s2.6 +/- .4 and 3.1 +/- .2 vs 2.0 +/- .3 for 40 and 44 kDa BP-3, respectively). Relative amounts of pituitary BP-2 tended (p<.1) to be greater in E than C ewes (2.6 +/- .3 vs 1.8 +/- .3). This increase was associated with a twofold increase in mRNA for BP-2 (p<.05) in E vs C ewes. Relative amounts of mRNA for LH beta were suppressed (p<.01) in E (7.4 +/- 2.3) compared to C ewes (19.5 +/- 3.0). No effect of estradiol was detected on relative amounts of mRNA for FSH beta and alpha subunit (p>.05), abundance of BP-2 and -4 in serum, and BP-3 and -5 in the pituitary (p>.1) amoung E and C ewes. In summary, estradiol increased serum BP-3 and pituitary expression of BP-2 and decreased expression of LH beta. Estradiol may influence gonadotrope function through mechanism(s) involving IGF and(or) BP's in the ovine.