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Glucocorticoids and Estrus in Swine. II. Plasma Concentrations of Estradiol -17β, Glucocorticoids and Luteinizing Hormone in Ovariectomized Gilts Given Estradiol Benzoate and Triamcinolone Acetonide^1,2,

University of Missouri⁵, Columbia 65211

Abstract

The effect of the synthetic glucocorticoid triamcinolone acetonide (TA) on estrous behavior and the hormonal pattern of'ovariecto-mized gilts given estradiol benzoate (EB) was examined. The proportion of gilts exhibiting estrus in response to .4 mg EB was reduced when 10 mg of TA was given in conjunction with estrogen (4 of 5 vs 0 of 4). After treatment with 10 mg TA, plasma glucocorticoid levels dropped to less than 1 ng/ml within 6 h and remained at this level for 5 d. Plasma corti-coid concentrations were unaffected by saline injection and ranged from 6 to 23 ng/ml during the post-treatment period. Plasma concentrations of estradiol-17β (E₂) increased to peak levels of 6 to 8 pg/ml between 8 and 24 h after injection of .4 mg EB. This response was not affected by TA. Plasma concentrations of luteinizing hormone (LH) were depressed by the EB injection from a pretreatment mean of 1.5 ng/ml to less than .9 ng/ml in both TA- and saline-treated gilts. An increase of LH 62 to 78 h after EB was observed in gilts given saline, but not in TA-treated gilts. Injection of 15 mg of TA reduced the proportion of gilts showing estrus after .8 mg of EB from 6/8 to 0/7. Eight hours after treatment with .8 mg EB and saline, peak plasma E₂ concentrations of 21.8 pg/ml were measured, but when 15 mg of TA was injected with .8 mg EB a lower peak of 7.6 pg/ml of E₂ was recorded. Plasma LH was depressed from 2.1 to .8 ng/ml by EB in both saline and TA-treated gilts. In gilts given EB and saline, LH remained below 1 ng/ml until a significant increase of LH occurred 56 to 78 h post-treatment. None of the gilts given TA and EB showed an increase in LH at this time. The synthetic glucocorticoid, TA, blocked estrus in ovariectomized gilts given EB and depressed endogenous corticoids for up to 5 d. Treatment with TA also resulted in lower levels of plasma E₂ in response to .8 mg of EB, but this alone does not appear to be responsible for the blocking of estrus because the plasma concentrations achieved were similar to those measured in saline-treated gilts showing estrus after .4 mg EB.

¹ Contribution from the Missouri Agr. Exp. Sta. Journal Ser. No. 8758.

² This investigation was supported part by Grant No. CSRS 701-15-44 from the USDA. The authors express appreciation to Darlene Bender and Betty Nichols for secretaria assistance.

³ Present address: School of Agriculture, Univ. of Nottingham, Sutton Bonington, Loughborough LE12 5RD, United Kingdom.

⁴ Present address: Dept. of Anim. Sci., North Carolina State Univ., P.O. Box 5127, Raleigh, NC 27650.

⁵ Dept. of Anim. Sci.