QUANTIFICATION OF THE CELLULAR PROLIFERATION ON FRESHLY DISPERSED CELLS FROM RAT ANTERIOR PITUITARIES AFTER INVIVO AND INVITRO LABELING WITH BROMODEOXYURIDINE

The labelling index i.e., the proportion of cells in S phase of the cell cycle, has been calculated in cytospin preparations of rat anterior pituitary cells after labelling either in vivo or in vitro with the thymidine analogue bromodeoxyuridine (BrdU). The aims of this work were (1) to check whether enzymatic digestion interferes with the incorporation of BrdU into S phase cells and/or whether it has any deleterious effect on the immunohistochemical detection of cells that have already incorporated BrdU, and (2) to check the viability of simultaneous staining for BrdU and markers for the different types of pituitary cells in the cytospins. No statistical difference was found between the labelling index after in vivo or in vitro labelling with BrdU. Identification of doubly-immunostained cells was straightforward and up to 40% of BrdU-labelled cells were immunopositive for pituitary hormones. It is suggested that cytospin preparations from biopsy samples may be used to study cellular proliferation without exposing the patient to the hazardous effects of BrdU infusion and without the interference of cell culture methods.