ISOLATION OF CELL-POPULATIONS FROM THE MARE CORPUS-LUTEUM - COMPARISON OF MECHANICAL AND COLLAGENASE DISSOCIATION

Corpora lutea were obtained from mares at days 3, 10 and 14 after ovul ation, and examined histologically. The morphology of isolated luteal cells obtained by either mechanical or collagenase dissociation of the tissue was examined and the cells stained to detect the steroidogenic enzyme Delta(5), beta-hydroxysteroid dehydrogenase. The ratio of larg e:small cells was significantly higher for cells obtained from mechani cally dissociated luteal tissue than for cells obtained by collagenase dissociation (P < 0.01). Cells obtained by both mechanical and collag enase dissociation secreted progesterone, although neither cell popula tion responded to exogenous gonadotrophin with an increase in progeste rone secretion. Homogenates of equine luteal tissue bound I-125-labell ed human LH with high affinity and specificity, and the specific activ ity and binding affinity of luteal LH receptors did not change signifi cantly from day 3, to days 10 and 14 after ovulation. However, mechani cally dissociated cells on days 10 and 14 bound significantly more LH than did collagenase-dissociated cells on these days (P < 0.05). These results indicate that (i) collagenase dissociation of mare luteal tis sue yields a population of cells that is unrepresentative of the corpu s luteum, and (ii) the mare corpus luteum is not responsive to LH in v itro at the stages examined.