RATE OF DECLINE IN CORTISOL CONCENTRATIONS IN OVARIAN FOLLICLES FOLLOWING ACTH TREATMENT IN THE SOW

The rates of decline in cortisol concentrations in blood and ovarian f ollicular fluid were assessed in cyclic sows (it = 30) after treatment with saline or a depot form of adrenocorticotrophic hormone (ACTH), A fter a single injection of ACTH (0.5 iu/kg, BW, IM), peak cortisol val ues were achieved in blood within 3 to 4 h followed by a half-life net clearance rate (t(1/2)) of 2.40 +/- 0.29 (SE) h, The same dose of ACT H was then given at 12 h intervals from days 9 to 13 of the estrous cy cle, On day 14 the concentrations of cortisol in follicular fluid were higher (P < 0.05) in ACTH-injected sows than in saline-injected contr ols, A t(1/2) value of 37.81 h was determined for cortisol based on th e decline in concentrations in follicular fluid collected on days 14, 16 and 18. This relatively slow rate of removal from developing ovaria n follicles may have implications for the previously observed detrimen tal effects of increased cortisol concentrations on follicular develop ment.