Size distribution of bovine steroidogenic luteal cells during pregnancy

This study was designed to investigate the size distribution of bovine ster oidogenic luteal cells throughout pregnancy. Corpora lutea collected from t hree different stages of pregnancy were used. Luteal tissue was dissociated into single-cell suspension by enzyme treatments. Cells were stained for 3 beta -hydroxysteroid dehydrogenase (HSD) activity, a marker for steroidoge nic cells. The steroidogenic cells covered a wide spectrum of size ranging from 10 to 60 mum in diameter. There was a significant increase in mean cel l diameter (P > 0.05) as pregnancy progressed. Mean diameter of 3 beta -HSD positive cells increased from 17.03 (s.e.1.3) pm in the cot-pus luteum of early pregnancy to 33.38 (s.e. 2.4) mum in the corpus luteum of advanced pr egnancy. The ratio of large (> 22 mum in diameter) to small (10 to 22 mum i n diameter) luteal cells was 0.32 : 1.0 in the early pregnancy, with the 10 to 22 mum cell size class predominant. However, the ratio of large to smal l lacteal cells was increased to 6.49 : 1.0 mum as pregnancy advanced and 2 3 to 42 mum cell sizes become predominant. It is likely that small luteal c ells develop into large cells as gestation progresses. Development of pregn ancy is associated with an increase in size of steroidogenic luteal cells.