Shifts in gonadotropin storage in cultured gonadotropes following GnRH stimulation, in vitro.

Stimulation of gonadotropes following castration or ovariectomy results in a shift in the gonadotrope population to cells that are mostly multihormonal. The purpose of these studies was to test this phenomenon, in vitro with the use of doublestains for LH and FSH applied to GnRH-stimulated gonadotropes. One-3 day monolayers were stimulated for 10 min-4 hr with 0.1 nM [D-Lys6] GnRH and then fixed and stained for both gonadotropins. After 60 min of stimulation, there was a significant increase in the proportion of gonadotropes that contained both hormones (from 57% to 74%) with a corresponding decrease in the proportion of cells that contained only one gonadotropin. There was no significant increase in the overall percentage of gonadotropes in the cell population indicating that the shift had probably occurred as a result of stimulation of the monohormonal gonadotropes to produce the other hormone. In addition, some of the stimulated gonadotropes showed the development of processes, some of which stained for only one of the gonadotropins. These data suggest that most gonadotropes may have the capacity to produce and store both hormones but they may perform these functions in separate regions of the same cell.