PROTEOGLYCAN PRODUCTION BY BOVINE GRANULOSA CELLS LN VITRO IS REGULATED BY CALMODULIN AND CALCIUM

Proteoglycan production by granulosa cells in vitro is regulated by gonadotropins. The objective of this study was to determine if FSH stimulation of proteoglycan synthesis was modulated by calmodulin or calcium. Assay for calmodulin using an ATPase assay dependent on calmodulin yielded concentrations of 7.7 microM. Bovine granulosa cells from follicles 1-9 mm diameter were incubated for 45 minutes in a chemically defined medium containing 5 microCi/ml 3H-glucosamine and various phenothiazine drugs which are inhibitors of calmodulin. In response to oFSH or rFSH at equivalent biological potencies, proteoglycan production decreased with increasing concentrations of phenothiazines from 1 to 50 microM. Addition of EGTA at 0.0, 0.5, 1.0 or 2.0 mM showed decreased proteoglycan production with increased amounts of the chelator. These data suggest that calmodulin and calcium are necessary for proteoglycan production by granulosa cells in response to FSH in vitro.