Does increased PGF2 alpha-receptor concentration mediate PGF2 alpha-induced luteolysis during early diestrus in the pig?
1995
Estill, C.T. | Britt, J.H. | Gadsby, J.E.
The mechanism by which multiple injections of PGF2alpha result in premature luteolysis in pigs is unknown. In the present study we evaluated whether PGF2alpha receptor concentrations on large luteal cells changed when gilts were injected IM with 12.5 mg of PGF2alpha every 12 hours from the morning of day 5 of an estrous cycle (estrus = day 0) until ovariectomy on day 6, 7, 8, or 9. Luteal PGF2alpha receptor concentrations remained constant from day 6 through 9 in the PGF2alpha-treated group, but increased linearly (P > 0.05) in control gilts from day 6 to 9. Receptor affinity for PGF2alpha did not change throughout the study in either PGF2alpha-treated or control gilts. Luteal progesterone concentrations were significantly lower in PGF2alpha-treated gilts than in control gilts only on day 9. Histological examination of luteal tissue obtained from PGF2alpha-treated gilts revealed definite evidence of luteolysis by day 8. We conclude that PGF2alpha-induced premature luteolysis is not mediated by an increase in luteal PGF2alpha receptor concentrations and, based on luteal progesterone concentrations and histological features, that the PGF2alpha-based protocol used to shorten the estrous cycle is accompanied by premature functional and structural luteal regression.
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