US EPA

6966015 

Journal Article 

REGRESSION OF INDUCED CORPORA-LUTEA IN MATURE CYCLIC GILTS BY HUMAN CHORIONIC-GONADOTROPIN 

Rampacek, GB; Kraeling, RR; Barb, CR; Estienne, CE; Estienne, MJ; , 

1992 

Yes 

Journal of Animal Science
ISSN: 0021-8812
EISSN: 1525-3163 

AMER SOC ANIMAL SCIENCE 

SAVOY 

3144-3148 

1429291 

WOS:A1992JQ07400027 

This study was conducted to determine whether chronic hCG treatment would cause regression of induced corpora lutea (CL) in mature cyclic gilts. Thirty-two mature gilts that had displayed one or more estrous cycles of 18 to 22 d were used. Sixteen gilts were hysterectomized (HYSTX) on d 6 to 9 (d 0 = onset of estrus) and their CL were marked with charcoal (spontaneous group). Sixteen gilts (induced group) were injected with 1,500 IU of pregnant mare's serum gonadotropin (PMSG) on d 6 and 500 IU of hCG on d 9 (day of hCG = d 0 of the induced cycle). Ovulation was assumed to occur on d 2 of the induced cycle. Induced gilts were HYSTX on d 8 to 9 (d 17 to 18 of the original spontaneous cycle) and their CL were marked with charcoal. Only gilts (n = 14) in which induced CL were present and in which the original CL had regressed were then subjected to treatment with saline or hCG. From d 10 to 29, gilts with spontaneous CL were injected daily with 500 IU of hCG (n = 8) or saline (n = 8). From d 10 to 29 of the induced cycle, induced gilts were injected daily with 500 IU of hCG (n = 6) or saline (n = 8). Jugular blood samples were collected every other day from all gilts beginning on the 1st d of daily hCG treatment and quantified for estradiol and progesterone by RIA. On the day after the last hCG injection, the number of charcoal-marked CL and charcoal-marked corpora albicantia (CA) were determined. All spontaneous CL were maintained. Six of eight gilts with induced CL that received saline maintained CL, whereas only one of six (P < .05) gilts with induced CL that received daily hCG maintained CL. All gilts that were treated with hCG had numerous accessory CL. Serum estradiol concentrations were < 5 pg/mL throughout the sampling period in gilts receiving daily saline injections. Serum estradiol concentrations in the hCG-treated gilts with spontaneous CL increased by d 12 and remained elevated. In the hCG-treated gilts with induced CL, serum estradiol concentrations were elevated from d 12 to d 22 but returned to control concentrations on d 24. These results indicate that daily administration of hCG caused regression of induced CL of mature cyclic gilts.