Evidence for Paracrine Interaction between Gonadotrophs and Lactotrophs in Pituitary Cell Aggregates*

Abstract

Pituitary cell aggregates prepared from 14-day-old male or female rats and maintained for 4-5 days in culture were superfused with LHRH during periods of 20 or 90 min. LHRH provoked a rapid and sustained rise of PRL release at concentrations similar to those stimulating LH release (10(-11)-10(-8) M). Dopamine, at a concentration inhibiting PRL release for 90%, weakened but did not prevent this stimulation. LHRH also stimulated PRL release in aggregates prepared from adult male rat pituitary cells, but the effect was weaker and seen only after a more prolonged period in culture. There was no PRL response to LHRH in aggregates of lactotroph-enriched populations, obtained by gradient sedimentation at unit gravity, in which only few and small gonadotrophs are present. When a lactotroph-enriched/gonadotroph-poor population was coaggregated with a highly enriched population of large gonadotrophs, LHRH very effectively stimulated PRL release, the extent of stimulation being dependent on the proportional number of gonadotrophs in the coculture. Superfusion of lactotroph-enriched/gonadotroph-poor aggregates with medium in which the gonadotroph-enriched aggregates had previously been incubated for 3 h with 1 nM LHRH (gonadotroph-conditioned medium) also provoked a clear-cut rise in PRL release. This effect was not due to LH, FSH, or the small amounts of PRL present in the gonadotroph-conditioned medium. The LHRH antagonist [D-Phe2-D-Ala6]LHRH was capable of blocking the PRL response to LHRH but not that to the gonadotroph-conditioned medium. In the lactotroph-gonadotroph coaggregates TRH stimulated PRL release but had no effect on LH release. TRH was also ineffective in releasing LH or FSH in populations containing both gonadotrophs and thyrotrophs. The present data suggest that gonadotrophs can activate the secretory activity of the lacotrophs through the release of a paracrine humoral factor.

History and perspectives of pituitary folliculo-stellate cell research

“…Insight into FS cell function had a new launch when, about two decades ago, Denef and co-workers identified FS cells as cells endowed with paracrine regulatory activities. During the search for a paracrine factor involved in lactotrope -gonadotrope communication (48,49), a factor was unexpectedly detected that caused the attenuation of secretion responses to either stimulatory (24) or inhibitory hormones (25) (see Table 1). This attenuating effect was more pronounced in cell aggregates obtained from low-density gradient fractions, in which FS cells (i.e.…”

Isolation and culture of somatotrophs from the pituitary of the rainbow trout: Immunological and physiological characterization

“…However, a single neuropeptide, neuroamine, or steroid can affect the activity of different cell types. Moreover, it has been demonstrated that dispersed cells aggregate under certain conditions to form a tissuelike configuration (Van Der Schueren et al, 1982) and that paracrine interactions can exist between particular cell types (Denef and Andries, 1983). In consequence, to study the mechanisms by which a regulatory factor influences the secretion of a certain hormone or to study the interactions between two functions, the cell type producing this hormone or implicated in these functions should be isolated.…”

Paracrine Control of Gonadotrophs by Somatolactotrophs through TRHinduced Follistatin Production

“…In patients with pituitary adenomas, TRH showed a stimulatory effect on FSH secretion [52,53]. However, in a study using pituitary cell aggregates, it has been shown that TRH was ineffective in releasing FSH [54].…”