Size distribution of bovine steroidogenic luteal cells during pregnancy

This study was designed to investigate the size distribution of bovine steroidogenic luteal cells throughout pregnancy. Corpora lutea collected from three 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 steroidogenic 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 cell 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 pregnancy. The ratio of large (> 22 mum in diameter) to small (10 to 22 mum in 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 small lacteal cells was increased to 6.49 : 1.0 mum as pregnancy advanced and 23 to 42 mum cell sizes become predominant. It is likely that small luteal cells develop into large cells as gestation progresses. Development of pregnancy is associated with an increase in size of steroidogenic luteal cells.