PARENT SESSION
SLIDE SESSION 21: FOLLICLE DEVELOPMENT: INPUTS TO FUNCTIONAL MATURATION
Chairs: Jeff May, Jerry Menon, Kari Doyle (Trainee)
Univ Ottawa-Lamoureaux 122
1:30 PM-3:30 PM

INCREASED OVULATION RATE IN GILTS TREATED WITH 5 - DIHYDROTESTOSTERONE.

Cardenas, Horacio¹, Pope, William¹, ¹

ABSTRACT- Treatment with testosterone has been shown to increase ovulation rate in swine. The present experiments were conducted to examine the involvement of the androgen receptor (AR) in ovulation rate by treating multiestrous gilts with the nonaromatizable AR agonist, 5 - dihydrotestosterone (DHT). Ovulation rate in response to daily i.m. injections of 0, 6, 60 or 600 g of DHT/kg BW, from Day 13 of the estrus cycle to estrus (Day 0), increased with each additional dose of DHT (P < 0.05). The average increase in number of corpora lutea ranged from approximately 3 to 17 over the three dosages. In an additional experiment, gilts treated daily with 60 g of DHT/kg BW during the early follicular phase, coincident with follicular recruitment (Day 13 to 16), or late follicular phase (Day 17 to estrus) had greater (P < 0.05) ovulation rates than those receiving vehicle, and were not different from gilts treated with DHT from Day 13 to estrus. Percent of recovered embryos on Day 3 was not altered (P > 0.05) when gilts were treated from Day 13 to 16 or Day 17 to estrus. Daily administration of 6 g of DHT/kg BW from Day 13 to estrus did not affect the relative amounts of AR mRNA but increased (P < 0.05) the amounts of follicle-stimulating hormone receptor (FSHR) mRNA in preovulatory follicles as determined by reverse-transcription polymerase chain reaction. Results suggest that androgen actions mediated by the AR appear to regulate factors associated to final follicular development and ovulation rate in swine. One of the roles of AR might be regulation of FSHR expression in ovarian follicles.

KEY WORDS: ovulation rate, FSH receptor, androgen receptor, swine