Regulation of ion transport in hypophysial pars intermedia follicular cell monolayers

We have previously reported that cultured monolayers of folliculo-stellate cells (FC) of adenohypophysial pars tuberalis (PT) and pars distalis (PD) origin express morphological and electrical properties typical of ion and fluid transporting epithelia. The objective of the present study was to examine whether cells expressing similar transport properties exist also in the pars intermedia (PI), an area of the adenohypophysis very poorly vascularized, where a cell type expressing such functions would be expected to play an especially significant role in the local regulation of the interstitial fluid content and circulation. Enzymatically and mechanically dispersed bovine pars intermedia fragments yield monolayers of polygonal, contact inhibited cells which rapidly develop domes. Such cells exhibit morphological features and growth properties very similar or identical to those expressed by cells previously identified af FC cells in PD and PT cultures. Similarly to their counterparts in the PD and PT, the PI FC display a potential difference and a resistance when mounted in Ussing chambers. Isoproterenol, prostaglandin E2, bradykinin and lysine vasopressin are able to stimulate active ion transport across FC monolayers. These data indicate that the PI contains ion transporting FC and suggest important local regulatory functions for these cells.