Flow cytometric immunofluorescence of rat anterior pituitary cells

We have developed a flow cytometric immunofluorescence technique for the quantification of growth hormone (GH), prolactin (PRL), and luteinizing hormone (LH) producing cells. The procedure requires about 24 hours and can objectively count 50,000 cells in about 3 minutes. It is based on indirect-immunofluorescence (fluorescein) of intracellular hormone using an EPICS V cell sorter. The fluorescein distributions are gated on DNA content (propidium iodide) to eliminate counting cell clumps. Cells from the same suspensions were stained immunocytochemically and counted microscopically (1,000-2,000 cells/sample). Immunofluorescence and immunocytochemistry correlated to within a few percent for GH and PRL cells. Cell suspensions from adult males and females with or without castration and a diethylstilbestrol (DES)-induced primary pituitary tumor were used to test the method. A major finding of this study was the objective identification of two populations of PRL producing cells, i.e., lightly and intensely stained cells. On the other hand, the fluorescence distribution of PRL cells from DES-induced pituitary tumors did not fall into two distinct populations but, rather, represented a broad continuum. This method should prove useful in studying the dynamics of pituitary cell populations under various physiological and pharmacological conditions.