Comparison of Induced Corpora Lutea from Prepuberal Gilts and Spontaneous Corpora Lutea from Mature Gilts: In Vitro Progesterone Production1

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Abstract
Prepuberal (P) gilts were induced to ovulate with pregnant mare serum gonadotropin followed 72 h later by human chorionic gonadotropin (hCG). Three P gilts and three mature (M) gilts each were ovariectomized on d 10, 14, 18, 22 and 26 (d 0 = day of hCG for P gilts and onset of estrus for M gilts). Gilts ovariectomized on d 14, 18, 22 and 26 were hysterectomized on d 6 to ensure maintenance of the corpora lutea (CL). Two to five grams of minced luteal tissue were dispersed using collagenase and hyaluronidase in HEPES buffered salt solution supplemented with glucose and bovine serum albumin. Dispersed cells were rinsed in Dulbecco's Modified Eagle Medium (DMEM), counted (ratio of large to total number of luteal cells determined) and then incubated for 1 h in DMEM. With aliquots standardized to 2.5 × 104 viable, large cells (>25 µm diameter) were incubated in 1 ml DMEM for 2 h in the presence of either 10, 50, 100 or 1,000 ng luteinizing hormone (LH); .1, 1, 10 or 100 ng hCG; 10, 100 or 1,000 ng norepinephrine (NE) or either .75, or 1.5 mM dibutyrl cyclic adenosine monophosphate (dbcAMP). Progesterone (P4) in the medium was quantified by radioimmunoassay. Basal P4 production (no P4 stimulator added to the medium) on d 10, 14, 18, 22 and 26 for P gilts was 246 ± 9, 66 + 4, 64 + 6, 41 ± 3 and 69 ± 6 ng/ml medium, respectively, and for M gilts was 281 ± 12, 128 ± 8, 53 ± 4, 82 ± 6, 101 ± 5 ng/ml medium, respectively. Luteal cells from M gilts were more responsive to LH, hCG and NE than those of P gilts on d 10 and 14 (P<.1), but there were no differences in large to total luteal cell ratios between induced and spontaneous CL. These results indicate that the induced CL of the prepuberal gilt are less sensitive to gonadotropins than the spontaneous CL of the mature gilt. Copyright © 1987. American Society of Animal Science . Copyright 1987 by American Society of Animal Science