Flow cytometric analysis and sorting of live female rat anterior pituitary cell types by forward angle and perpendicular light scatter: effect of 17 beta-estradiol.

Administration of physiological concentrations of 17 beta-estradiol (E2) to ovariectomized rats resulted in changes in the forward angle light scatter (FALS) and perpendicular light scatter (PLS) signals of anterior pituitary lobe cells. One day after steroid treatment some cells showed increases in PLS signals to an intermediate ridge position lying between the two ridges seen for cells prepared from oil-treated ovariectomized rats. Over the first 5 days of E2 treatment, the major effect was a progressive increase in the FALS signal of cells in this intermediate ridge position. Increases in PLS signals continued over the 12-day treatment period. Since the results of a cell sorting experiment showed that PRL cells predominated in the intermediate scatter ridge, it was concluded that E2 increases both size (FALS) and secretory granule content (PLS) of mammotrophs. Cells in the low and high scatter regions were unaffected by E2. Those in the low scatter region were shown, by both electron microscopy and light microscopic immunochemistry, to be enriched in agranular, unstained endothelial-follicular cells. The high-scatter region contained predominantly GH cells. Administration of E2 to pituitary cells cultured in serum-free or serum-containing media for 1-12 days had no effect on the FALS-PLS bivariate distribution. However, the light scatter ridges produced from cells in culture were compressed into a single ridge of narrow PLS and broad FALS signal intensity with increasing time in culture.