Endocrine Abstracts

Folliculo-stellate (FS) cells exert a paracrine regulation on their neighbouring endocrine cells in the anterior pituitary gland. FS cells are non-granular cells characterized by long cytoplasmic processes and form follicles with microvilli on their luminal cavity, suggesting a transport function. Moreover, FS cells form monolayers in primary culture and develop domes after reaching confluence, characteristics of polarized transport epithelia. However little is known about transporter proteins in FS cells. We investigated the expression of three transporters: the peptide transporter PepT2, the glucose transporter 2 (Glut2) and the cholesterol and annexin one transporter ATP-binding cassette transporter A1 (ABCA1) in two FS cell lines (TPit and TtT/GF cells), CaCo2 cells (a positive control epithelial colorectal cell line) and anterior pituitary by immunogold electron microscopy and western blotting. Immunogold particles for each of the transporters investigated were detected in Caco-2 cells. TPit, TtT/GF and anterior pituitary cells were found to express ABCA1, Glut2 but not PepT2 and the same findings were obtained in FS cells in rat anterior pituitary. In response to changing physiological demands during pregnancy, the pituitary has the ability to expand its cell number several fold and FS cell transport systems may be important for supporting these changes. Therefore FS cell size and ultrastructure were studied by use of electron microscopy in virgin and pregnant (1 and 3 weeks) rats. FS cell size was significantly increased in 3 weeks pregnant rats (P<0.01) with more numerous microvilli compared to virgin rats and an increased number (P<0.01) of FS cells were located adjacent to blood. In weaned rats FS size was not significantly different to virgin. An increase in Glut2 immunogold labelling of FS cell microvilli was measured in 3 weeks pregnant pituitary consistent with a role for FS cells in supporting increased nutrient requirements for pituitary growth in pregnancy.