Evidence for Functional Communication between Folliculo-Stellate Cells and Hormone-Secreting Cells in Perifused Anterior Pituitary Cell Aggregates*

Abstract

Dispersed anterior pituitary cells from adult female rats were separated by gradient sedimentation at unit gravity. The small-sized cell population on top of the gradient consisted of 65.6 +/- (SE) 4.2% (n = 8) cells immunoreactive to antiserum against S-100 protein, a marker of folliculo-stellate (FS) cells in rat pituitary. The corresponding fraction derived from adult male or immature female rats were also enriched in S-100 positive cells but to a lower extent. Only small numbers of S-100 positive cells were found in medium- and large-sized cell populations. Coaggregating the S-100 cell-enriched populations from adult females with other pituitary cell populations resulted in a clear-cut inhibition of the GH response to rat GH-releasing factor and beta-adrenergic agents, of the PRL response to TRH and angiotensin II (AII) and the LH response to LHRH. The magnitude of inhibition increased with the number of FS cells put into the coaggregates. In perifused aggregates prepared from different gradient fractions from immature females, there was a negative correlation between the occurrence of FS cells and the magnitude of the PRL response to AII. The low responsiveness to AII in FS cell enriched aggregates was not abolished when these aggregates were redissociated into single cells. It is suggested that FS cells constitute an intercellular messenger system for local inhibitory control of pituitary hormone secretion which is not based on direct and intimate contact between the interacting cells.

History and perspectives of pituitary folliculo-stellate cell research

“…In vitro studies using static monolayer cultures, with pituitary cells (46) or enriched FS cells (23) plated at high density, resulted in the formation of confluent monolayers and also 'tight' diffusion barriers and dome formation (23). In our studies, however, we used three-dimensional (3D) re-aggregated cell cultures, obtained by gyratory shaking of isolated pituitary cells in suspension, yielding a more histotypic cell culture system of the rat anterior pituitary (24,25). Permeability studies of the interstitial environment in FS cell-enriched cell aggregates (47) confirmed the leakiness of intercellular junctions in vitro, similar to intercellular junctions in the rat anterior pituitary in situ (3,26,45).…”

“…The electrophysiological properties of presumed FS cells have been studied in detail in the amphibian Xenopus laevis (22). Older studies have especially focussed on the transport epithelial characteristics of FS cells (23) and the contribution of FS cells to the regulation of the pituitary interstitial environment (23), and to paracrine communication with pituitary hormone-secreting cells (24,25).…”

Interleukin‐6 an endocrine cytokine

“…Folliculo-stellate cells do not secrete hormones and have characteristics in common with monocytic phagocytes. Initially believed to be inert cells there is evidence that folliculo-stellate cells secrete substances including IL-6 which are involved in the paracrine control of hormone secretion (Baes et al, 1987). There is no direct evidence at present that IL-6 is synthesized or released by any of the normal hormone secreting cells.…”

A Role of Pituitary Adenylate Cyclase Activating Polypeptide(PACAP) as a Regulator of Paracrine Interactions between Folliculo-Stellate Cells and Gonadotropes through the Control of Activin-Follistatin Interactions.

“…Therefore, it is not reasonable to rule out the possibility that increased physical connection between TtT/ GF cells and gonadotropes in PACAP-treated co-cultures underlay the paracrine action of PACAP-treated TtT/GF cells. However, this possibility appears minimal because of the results from experiments using CM and by analogy that physical connection between FS cells and growth hormone/prolactin-secreting cells does not mediate the functional communications between these cell types [1]. On the other hand, the effect of PACAP on normal gonadotrope cell growth is not clear, although PACAP stimulates proliferation of αT3-1 cells [32], a transformed cell line that express α-subunit, but not β-subunit, genes of gonadotropins [39].…”