Effect of intraovarian factors on porcine follicular cells: cumulus expansion, granulosa and cumulus cell progesterone production

The role of granulosa cell conditioned media (CM) containing luteinization stimulator (LS). and the role of EGF in the cumulus expansion of oocyte-cum ulus complexes (OCC) isolated from large antral follicles was investigated. The CM were prepared by incubation of granulosa cells isolated from large antral follicles. After 24 h incubation, more than 61 or 64% of OCC expande d to the +3 and +4 stage in the presence of CM (50%) or EGF (10 ng/ml), res pectively. The stimulatory effect of LS and ECF on the cumulus expansion wa s accompanied by the enhanced hyaluronic acid synthesis. Complete suppressi on of cumulus expansion stimulated by LS and EGF was observed in the presen ce of 10 mu mol/l genistein (tyrosine kinase inhibitor), in the presence of 10 mmol/l LiCl (the inhibitor of inositol 1,4,5-trisphosphate metabolism), and 100 mu mol/l gallopamil, verapamil and norverapamil (calcium channel b lockers). Stimulatory effect of EGF on the cumulus expansion of OCC isolate d from large follicles was accompanied by the increased cumulus cell proges terone production. However, EGF did not affect the progesterone production by OCC isolated from small follicles. To determine whether EGF could modula te the granulosa cell steroidogenesis also, the effect of EGF on granulosa cells isolated from large (LGC) and small (SGC) follicles was compared. EGF (10 ng/ml) failed to affect the progesterone synthesis during 72 h culture of SGC but significantly enhanced the LGC progesterone production. Our res ults indicate that luteinization factor stimulates the cumulus expansion an d hyaluronic acid synthesis by the OCC isolated From large antral follicles . The mechanism of LS- and EGF-induced cumulus expansion may involve tyrosi ne kinase activation and calcium mobilization. In addition, these results i ndicate the different response of porcine cumulus and granulosa cells origi nating from small and large follicles on the stimulatory effect of EGF (C) 2001 Elsevier Science B.V. All rights reserved.