J. Anim Sci.
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J. Anim Sci. 1984. 59:1295-1302.
© 1984 American Society of Animal Science
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Follicular Growth and Production of Estrogen and Progesterone After Injection of Gilts with Human Chorionic Gonadotropin on Day 12 of the Estrous Cycle

H. D. Guthrie1, 2, and J. F. Knudsen3

US Department of Agriculture, Beltsville, MD 20705

Abstract

Twenty cyclic gilts were injected im with either saline (control) or 1,000 IU of human chorionic gonadotropin (hCG) on d 12 of the estrous cycle to determine the effects of hCG on follicular development and steroidogenesis. Blood was collected when gilts were sacrificed on d 13 or 16. Follicles were classified as medium (3 to 6 mm in diameter) or large (=6 mm diameter), dissected from the ovary, measured and weighed. Pieces of follicle wall were incubated 3 h in Krebs Ringer bicarbonate buffer (KRB) on ice in an atmosphere of air or at 37 C in an atmosphere of 95% O2:5% CO2. Unconjugated estrogen and progesterone in blood plasma, follicular fluid and 10,000 x g supernatants of incubated follicular tissue homogenates were quantified by radioimmuno-assay. On d 13 follicles on ovaries of control or hCG-injected gilts were <6 mm in diameter. On d 16, one of five control gilts had some large follicles, while all five hCG-treated gilts had large as well as medium follicles. On d 16 follicular fluid of large follicles from hCG-injected gilts contained twofold more estrogen and 40-fold more progesterone than medium follicles on the same ovaries. Tissue from large follicles of hCG-injected gilts produced more progesterone in vitro than did tissue from medium follicles (P<.05), but estrogen production did not differ. On d 16 medium follicles from control or hCG-injected gilts were larger, contained more estrogen and less progesterone than those recovered on d 13 (P<.01). However, medium follicles on d 13 and 16 from hCG-injected gilts were larger and their fluid contained more estrogen and progesterone than medium follicles from control gilts (P<.01). This study demonstrated that 1,000 IU of hCG injected on d 12 of the estrous cycle in the gilt resulted in development of large follicles, resembling preovulatory follicles at the onset of estrus before the preovulatory luteinizing hormone surge.

Footnotes

1 Reprod. Lab., Anim. Sci. Institute, Beltsville Agr. Res. Center, ARS.

2 Mention of a trade name, proprietary product, or specific equipment does not constitute a guarantee or warranty by the USDA and does not imply its approval to the exclusion of other products that may be suitable.

3 Current address: Good Samaritan Hospital, Lochraven Building, Baltimore, MD.






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Copyright © 1984 by the American Society of Animal Science.