PARENT SESSION
PLATFORM SESSION 21: REGULATION OF GONADOTROPINS AND THEIR RECEPTORS: II
Chair: LaBarberra, Andrew¹, ¹
Co-chair: Meehan, Thomas¹, ¹
Harborside D
2:00 PM-4:00 PM

(455) EFFECTS OF AN AROMATASE INHIBITOR ON TESTICULAR STEROIDS AND GONADOTROPINS IN ADULT AND NEONATAL BOARS.

At-Taras, Eeman¹, Berger, Trish¹, Roser, Janet¹, ¹ Dept of Animal Science, Davis, CA

ABSTRACT- Boars have relatively high concentrations of estrogen compared with males of most species. The objective of this study was to investigate the impact of reducing estrogen concentrations on testicular steroids and gonadotropins in adult and neonatal boars. Adult boars (ages 14 to 16 months) were treated with a one-time oral dose of a nonsteroidal aromatase inhibitor (inhibits conversion of androgens to estrogens) at 0.1 or 1.0 mg/kg BW. Adult boars were bled via jugular venipuncture at 0 (prior to treatment), 24, 48 and 168 hours. In addition, one-week-old boars were treated orally at weekly intervals for 3 weeks with vehicle (control) or 0.1 mg/kg BW of the aromatase inhibitor. Blood was drawn weekly via jugular venipuncture prior to oral treatment. Plasma samples from both adult and neonatal boars were analyzed for estradiol (E₂), estrogen conjugates (EC), testosterone, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) levels by valid RIA. Concentrations of E₂ and EC declined dramatically within the first 24 hours of treatment from 465.39±116.03 to 36.71±11.48 pg/ml and 34.43±2.51 to 4.15±1.22 ng/ml, respectively (p=0.001). E₂ and EC concentrations remained low up to 168 hours post-treatment. Concentrations of testosterone, follicle stimulating hormone (FSH) and luteinizing hormone (LH) remained unchanged in these boars. E₂ concentrations in neonatal treated boars decreased compared with levels in control littermates (p=0.006). At 2 weeks of age E₂ concentration was 39.93±5.85 pg/ml in controls and only 19.05±4.25 pg/ml in treated boars. Testosterone concentrations in treated boars were significantly higher than levels in control littermates (p=0.034). At 3 weeks of age testosterone concentrations were 1.14±0.13 ng/ml in treated boars and only 0.796±0.057 ng/ml in controls. FSH concentrations were higher in treated boars than in their control littermates (p=0.02). There was no difference in concentrations of LH between control and treated boars. In summary, aromatase inhibition affects the hormone milieu in adult and neonatal boars differently. Neonatal boars appear to be more sensitive to aromatase inhibition than adult boars. This may be important for early testicular development.

KEY WORDS: Aromatase inhibition, boars, testicular steroids, gonadotropins