Follicle growth in hypophysial stalk-transected pigs given pulsatile GnRH and pregnant mare serum gonadotropin

In experiment 1, nine prepuberal crossbred gilts 145 +/- 2 days of age and 90.3 +/- 1.6 kg body weight (BW) were hypophysial stalk-transected (HST) or sham-HST. Starting at 0800 on Day 1 (35 +/- 2 days after surgery), three sham-HST and two HST gilts received 3.5% sodium citrate vehicle (V) while two HST gilts and two sham-HST gilts received pulses of 2.5 micrograms GnRH every 45 min for 9 days via a jugular vein cannula. At 0800 on day 7, all gilts received 1,000 IU of pregnant mare serum gonadotropin (PMSG) im. Blood was sampled every 15 min from 0800 to 0845 on Days 1 through 6. On Day 10, ovarian morphology and ovarian and follicular fluid weights were recorded. In experiment 2, eight prepuberal crossbred gilts, 146 +/- 6 days of age and 79.5 +/- 1.5 kg BW, were HST or sham-HST. Starting at 0800 on Day 1 (7 +/- 4 days after surgery), two sham-HST and three HST gilts received V, while three HST gilts received pulses of 2.5 micrograms GnRH every 45 min for 8 days. At 1200 on Day 5, all gilts, including three unoperated controls (UC), received 1,000 IU of PMSG im. Blood was sampled from all but UC gilts every 15 min from 0800 to 0845 on Days 1 through 5. Ovarian data were obtained on Day 9. The HST + V gilts failed to respond to PMSG, whereas growth of ovulatory follicles was stimulated in the other groups in both experiments.(ABSTRACT TRUNCATED AT 250 WORDS)