Hypothalamic peptides affect the ratios of GH and PRL cells: role of cell division.

In the present study, we attempted to ascertain whether the differential effects of hypothalamic peptides (GRF, LHRH, CRF, TRH) on the proportions of GH and PRL secreting cells in culture were dependent upon cell proliferation. This was accomplished by chronically exposing rat pituitary cells to selected hypothalamic peptides in the presence or absence of cytosine arabinoside (an inhibitor of cell proliferation) and then measuring hormone release by plaque assays. Our results suggest that the effects of these peptides on the percentages of GH and PRL cells are manifest via both proliferation-dependent and proliferation-independent mechanisms.