IN-VITRO MODIFICATIONS IN THE PROLIFERATION RATE OF PROLACTIN CELLS ARE ACCOMPANIED BY NUCLEAR MORPHOMETRIC VARIATIONS

In order to establish the correlation between in vitro proliferation r ate and morphometric variations of prolactin immunoreactive cells, a m orphometric study was carried out in rat pituitary monolayer cultures by means of the double immunocytochemical staining methods employing m ouse monoclonal antiproliferative cell nuclear antigen (PCNA) and rabb it anti-prolactin (PRL) as primary antibodies. PCNA was found to be an adequeate marker for proliferation in pituitary monolayer cultures. 4 8.35+/-2.78% of the cells present in the culture were in active cell c ycle after 3 days of incubation and a similar proportion, 54.93+/-2.83 % was found after 7 days. On the 3rd day, PRL immunopositive cells acc ounted for 15.16+/-0.21% of the total cellular content in the dishes a nd 8.68+/-0.12% of the PCNA immunoreactive cells were also PRL immunop ositive cells and, 60.95+/-2.65% of PRL cells stained for PRL and PCNA . On the 7th day, an increase to 32.18+/-0.60% of PRL cells was found; the PCNA and PRL cells accounted for 60.32+/-2.34% of the total PRL c ells, and 19.88+/-1.09% of the PCNA reactive cells stained for PRL. Ad ditionally, the morphometric analysis performed after 3 or 7 days of i ncubation showed that, while the size of PRL cells remained unmodified , the nuclear area had increased on the 7th day in relation to the 3rd day (p<0.01). These results suggest: 1) PCNA is a valid proliferative marker for pituitary cells in cultures; 2) a very high percentage of the PRL cells was in early proliferation; 3) on the 7th day of incubat ion, the proliferative rate of PRL cells was very similar to that obse rved on the 3rd day, suggesting a maintained proliferation for PRL cel ls at early incubation phases; and 4) the cellular activity, expressed as variations in the nuclear size, was higher on the 7th day than on the 3rd day; in addition, the numerical density of PRL cells increased .