Plasma cortisol and progesterone concentrations, uterine proteins and corpora lutea LH/hCG binding characteristics in gilts following adrenocorticotropin or hydrocortisone acetate administration during diestrus

In a preliminary study four gilts fitted with jugular cannula were injected once or twice daily with either 2 mg hydrocortisone acetate (HA) in sesame oil per kg body weight, intramuscularly (IM) or 1 I.U. adrenocorticotropin (ACTH) in 14% gelatin per kg body weight, subcutaneously (SQ). Twice daily injection of ACTH significantly elevated (P<.05) plasma cortisol levels above that of the control animals (injected with 2 ml sesame oil, IM and 2 ml 14% gelatin, SQ, twice daily). Hydrocortisone acetate did not significantly elevate cortisol levels, although a second injection appeared to elicit a heightened cortisol response. Twenty-three gilts were assigned to the following treatments administered twice daily at dosage levels established in the preliminary study; (1) nonbled control; (2) bled control, injected with the hormone carriers; (3) HA; and (4) ACTH. Treatments were administered days 2 through 7 (period one) or days 8 through 13 (period two) of the estrous cycle, with plasma samples collected daily during treatment and ovariectomies performed and uterine flushings obtained the day following the final day of treatment. For both periods of treatment ACTH decreased and HA increased cortisol levels in a linear fashion over the days of treatment compared to the quadratic response of the bled controls. Within period two both HA and ACTH treatment resulted in a linear increase in progesterone levels compared to the quadratic pattern of the bled controls; however, there was no significant effect of treatment upon progesterone profile compared to the controls in period one. There were no significant differences between the nonbled and bled controls for any of the day 8 or 14 parameters measured, therefore the controls were pooled by period and all comparisons made relative to these pooled controls. There were no differences due to treatment detected within period one for either total uterine proteins or corpora lutea (CL's) luteinizing hormone/human chorionic gonadotropin (LH/hCG) receptor binding affinity or capacity. Within period two ACTH treatment reduced (P<.05) uterine proteins compared to the pooled controls, whereas HA had no effect. There was a trend (P<.10) for day 14 CL's LH/hCG receptor binding affinity to be reduced by HA and ACTH treatments although binding capacity was unaffected. Corpora lutea LH/hCG receptor binding affinity and capacity were negatively (P<.05) correlated. Based upon these data, mid- to late diestrus appears to be a physiological state sensitive to the HA and ACTG treatment used in this study. Total uterine proteins were reduced by ACTH treatment, which suggests that the uterine environment was altered. Since a proper uterine environment is essential for the survival of many embryos, alteration of uterine proteins by ACTH may effect embryonic survival.