EXPRESSION OF THE IGF SYSTEM IN PRIMARY AND IMMORTALIZED PORCINE OVARIAN GRANULOSA-CELLS

We have established a novel granulosa cell line derived from porcine o varian follicles (4-6 mm in diameter). This cell line, MDG2.1, was obt ained by transfection of freshly cultured cells with the plasmid pSV3n eo. Doubling time for MDG2.1 cells is 24-36 h. Northern analysis for R NAs of the insulin-like growth factor (IGF) regulatory system indicate s that RNAs for IGF-I, IGF-I receptor, and IGF binding proteins (IGFBP ) 2-6, but not IGFBP-1, are expressed in MDG2.1 cells. The secretion o f IGFBPs from MDG2.1 cells shows > 10-fold levels of the 24 kDa form, reduced secretion of other IGFBPs, with no change in the total amount of IGFBP secreted, as compared to primary cells cultured under identic al conditions. Use of endoglycosidase F indicated that several IGFBPs are posttranslationally modified. This cell line is a useful model and plasmid transfection target system to investigate IGFBP action in ova rian granulosa cells.