[Morphological and functional changes in 3 beta-HSD positive cells in corpora lutea during pregnancy in rats]

On days 5, 10, 15 and 20 of pregnancy, rat corpora lutea (CLs) were dissected and dissociated into single cell suspensions by enzyme treatments. To assess 3 beta-hydroxysteroid dehydrogenase (HSD) activity, a histochemical suspension-staining procedure was used. The number of cells positive for 3 beta-HSD in CL were 148.0 +/- 13.7, 130.1 +/- 25.4, 134.0 +/- 23.5 and 116.8 +/- 13.5 X 10(3) cells on days 5, 10, 15 and 20 of pregnancy, respectively. The 3 beta-HSD positive cells increased in size from 18.5 +/- 0.28 microns on day 5 to 35.7 +/- 0.50 microns on day 20 of pregnancy. The suspended luteal cells were incubated in serum-free DME-F12 for 20 hours with or without human chorionic gonadotropin (hCG, 100 ng/ml) or dibutyryl cyclic AMP (dbcAMP, 10mM) to test their functionality, and progesterone accumulation was determined by radioimmunoassay. Progesterone secretion from the 3 beta-HSD positive cells was maintained at the same levels until day 15 and decreased significantly on day 20 of pregnancy. However the response to hCG stimulation of the 3 beta-HSD positive cells decreased significantly on day 20, the 3 beta-HSD positive cells maintained the same responsiveness to dbcAMP stimulation on progesterone secretion throughout pregnancy. These data suggest that the steroidogenic rat luteal cells may be regulated by morphologically and functionally different mechanisms, and that progesterone may be secreted by at least two different pathways.