Effects of GnRH and ionic environment on the secretion of LH, FSH and prolactin by dispersed sheep pituitary cells.

Dispersed sheep adenohypophysial cells were used to study the effects of GnRH and ionic environment on LH, FSH and PRL release. The cells were used immediately after they were dissociated from the glands by a combination of gentle mechanical agitation and enzymatic digestion. GnRH caused a log-dose related release of LH and FSH with minimal and maximal effective doses of 10 pg ml-1 and 100 pg ml-1, respectively. Elevated level of K+ stimulated LH, FSH and PRL release. Maximal response was observed with the doses of 30--60 mmol l-1 K+ for LH and FSH, while a dose of 120 mmol l-1 was required for PRL release. The removal of Ca2+ by the addition of EDTA did not affect basal LH and FSH release but resulted in an increase of PRL release. It also abolished the release of LH and FSH induced by GnRH or by a high level of K+ but did not prevent a small and significant additive effect of K+ and GnRH. The release of PRL induced by a high level of K+ was inhibited by Ca2+ removal, but was not completely prevented at the highest K+ concentration used. The results demonstrated that the cells retained their responsiveness to secretagogues for LH, FSH and PRL immediately after dispersion.