ENHANCEMENT BY PROLACTIN OF THE GNRH-INDUCED RELEASE OF LH FROM DISPERSED ANTERIOR-PITUITARY-CELLS OF THE BULLFROG (RANA-CATESBEIANA)

The response bf enzymatically dispersed anterior pituitary cells of th e bullfrog (Rana catesbeiana) to gonadotropin-releasing hormone (GnRH) was studied by monitoring the release of luteinizing hormone (LH) int o the culture medium. The cells responded to GnRH by releasing LH acco rding to the incubation time and to the GnRH concentration. The respon siveness to GnRH became less conspicuous as the cell density was reduc ed. Addition of prolactin (PRL) to the medium enhanced the responsiven ess to the secretagogue, and addition of antiserum against PRL lowered the responsiveness to a certain extent. Immunohistochemical studies o f sectioned pituitaries revealed that PRL cells most frequently locate d in contact with LH cells. The possibility that PRL acts directly on gonadotrophs to enhance their responsiveness to GnRH was suggested. (C ) 1997 Academic Press.