Size distribution of steroidogenic and non-steroidogenic ovine luteal cells throughout pregnancy

Abstract

The present study examines the size distribution of ovine steroidogenic and non-steroidogenic luteal cells throughout pregnancy. Cells were isolated from corpora lutea collected from early (:! 8 weeks), mid (9 to 14 weeks) or late (15 to 18 weeks) stages of pregnancy. Cells were stained for 3,3beta-hydroxysteroid dehydrogenase (3beta-HSD) activity, a marker for steroidogenic cells. Both 3beta-HSD positive and beta-HSD negative cells covered a wide spectrum of size ranging from 7 to 37mum in diameter. There was a significant increase (P > 0.01) in mean diameter of nonsteroidogenic luteal cells as pregnancy progressed. Mean diameter of 3beta-HSD negative cells increased from 17.8 (s.e. 0.4) mum in the corpus luteum of early stage of pregnancy to 22.4 (s.e. 0.3) mum in the corpus luteum of advanced pregnancy. However, there was no significant increase in the mean diameter of 3beta-HSD positive cells. Corpora lutea obtained from early stages of the pregnancy contained more steroidogenic cells than the cells obtained from mid and late pregnancy (P < 0.01). Percentage of 3beta-HSD negative cells had increased 2.07-fold by 18 weeks of pregnancy when compared with the early stage of pregnancy. In contrast, percentage of 3,3beta-HSD positive cells had decreased to 50% of starting values during the same period (P < 0.05). These results indicate that the ovine corpus luteum of pregnancy is morphologically dynamic over the course of pregnancy. Steroidogenic activity of luteal cells may decrease as pregnancy progresses, especially activity of the large luteal cells.