Characterization of Two Steroidogenic Cell Types in the Ovine Corpus Luteum1, 2

Publisher Website
Google Scholar
Abstract
A procedure which utilized elutriation was developed which permitted the separation of 2 populations of luteal cells from enzymatically dispersed corpora lutea taken from superovulated ewes on the 10-12th day of the estrous cycle. One population consisted of cells which measured 23-35 .mu.m in diameter, while the other consisted of cells with a diameter of 12-22 .mu.m. Preparations of both cell types were analyzed for rate of secretion of progesterone, responsiveness to secretagogues and number of specific binding sites for luteinizing hormone/human chorionic gonadotropin (LH/hCG), and prostaglandins E2 and F2.alpha.(PGE2 and PGF2.alpha.). Without stimulation, the secretion of progesterone by large cells was .apprx. 20-fold greater than for an equal number of small luteal cells. The ability of large luteal cells to respond to LH (100 ng/ml) or N6,O2-dibutyryl cAMP (dbcAMP, 10 mM) was minimal and .apprx. 10% of that obtained with small luteal cells. Marked differences were also observed between the 2 cell types with respect to the number of specific binding sites for LH/hCG, PGE2 and PGF2.alpha.. The large cells had very few receptors for LH/hCG compared to small cells (3074 receptors/large cells vs. 33,260/small cell during the breeding season). The majority of receptors for PG was found in large cells (68,143 sites of PGF2.alpha. and 10,955 sites for PGE2/large cells; 2115 sites for PGF2.alpha. and 904 sites for PGE2/small cell). Apparently, functional differences exist between the large and small steroidogenic cells in the corpus luteum of the ewe. The large luteal cells appear to secrete most of the progesterone produced by the corpus luteum, however, this secretion appears to be independent of LH and dbcAMP. The small luteal cells secrete minimal quantities of progesterone in the unstimulated state but respond dramatically to LH or dbcAMP.