CHARACTERIZATION OF RAT PITUITARY-CELLS BY THEIR RESPONSES TO HYPOTHALAMIC RELEASING HORMONES

Rat pituitary cells in monolayer culture were characterized by their [Ca2+]i responses to hypothalamic releasing hormones, growth hormone-releasing hormone (GHRH), thyrotropin-releasing hormone (TRH), gonadotropin-releasing hormone (GnRH) and corticotropin-releasing hormone (CRH). The percentages of the cell population responding to GHRH, TRH, GnRH, CRH and non-responding cells were 27.3%, 47.6%, 13.8%, 6.2% and 35.3%, respectively. Some of the cells responded to two or more of those hormones. In the GHRH-responding cells, the population of TRH-responding cells was 51.4%, In the TRH-responding cells, the population of GHRH-responding cells was 30.8%. Some of the GHRH-responding cells also responded to CRH and GnRH. In the GnRH-responding cells, the population of TRH-responding cells was 61.8%. In summary, GHRH-responding cells have an especially close relationship with TRH-responding cells, and GnRH-responding cells also have close relationship with TRH -responding cells. There is also some relationship between the populations responding to other pairs of releasing hormones. These findings suggest functional overlapping among each population of pituitary cells. (C) 1994 Academic Press, Inc.