Various investigations were performed to examine how androgens might influence reproduction in gilts. The first investigation was designed to begin to address the endocrinology of how androgens increase ovulation rate in gilts when administered during the follicular phase. Gilts were injected with androgen receptor agonists (5α-dihydrotestosterone, DHT or testosterone), antagonist (flutamide) or a combination of both from day 13 of the estrous cycle (day 0= onset of estrus) until the onset of estrus. Hourly blood samples were collected when treatments were initiated until the onset of estrus. Testosterone or DHT treatments increased (P<.05) mean concentrations of FSH in serum and this effect was blocked by co-treatment with androgens and flutamide (an androgen receptor antagonist). This augmentation of FSH secretion occurred without altering the rate of luteolysis (as determined by progesterone concentrations) or induction of consistent changes on luteinizing hormone. Estradiol-17β and androstenedione concentrations augmented (P<.05) after 2 hours of injections of testosterone even when flutamide was present. Treating gilts with androgens decreased embryonic survival and co-treating gilts with androgens and flutamide reversed these effects. Results of this experiment indicate that androgen actions, mediated by the androgen receptor, increased FSH concentration and this increase might be related, in part, to the previously observed increase in ovulation rate.
The second investigation comprised two experiments and was conducted to examine the effects of androgens on neonatal development of the uterus. A total of sixty gilts were utilized. In Experiment 1, twenty four newborn gilts were assigned randomly to increasing dosages of DHT (0, 6, 60 or 600 µg per kg of body weight) from birth (postnatal day, PND 0) to PND 13. Treating gilts with increasing dosages of DHT did not alter any of the components of uterine development examined on PND 14 (wet weights of the uterus, liver, heart or longissimus dorsi, endometrial thickness, height of luminal epithelium, glandular penetration nor myometrial thickness). In Experiment 2, thirty six gilts were utilized to investigate up to 14 days of age the effects of androgens on estrogenic-induced stimulation of uterine development. Gilts were randomly assigned at birth to receive daily injections of vehicle, 50 µg of estradiol valerate, 60 µg of DHT, 10 mg of flutamide, estradiol valerate plus DHT or estradiol valerate plus DHT plus flutamide, per kg of body weight, from PND 0 to PND 13. Treatment of neonatal gilts with estradiol valerate increased uterine wet weight, endometrial thickness, glandular penetration and myometrial thickness but only the estradiol valerate-induced effects on myometrial thickness were blocked by co-treatment with DHT. Results of these experiments indicate that within the first two weeks of age, androgen treatment failed to influence most of the estrogenic-induced stimulatory effect as has been observed in the adult uterus.