DEVELOPMENT OF A BIOASSAY FOR FSH USING A RECOMBINANT HUMAN FSH RECEPTOR AND A CAMP-RESPONSIVE LUCIFERASE REPORTER GENE

FSH exerts its actions primarily by increasing cAMP levels via a G protein-linked transmembrane receptor. We report the development of a bioassay for FSH using a cell line that stably expresses the human FSH receptor and a cAMP responsive human glycoprotein hormone ct subunit luciferase reporter construct. Receptor activation by FSH was measured by changes in luciferase activity. The cell line was shown to express 1.6 X 10(4) receptors per cell which bound FSH with high affinity (K-d 2.76 x 10(-9) M). Human pituitary FSH caused a dose-dependent increase in cAMP (ED(50), 190 mIU/ml) and luciferase (ED(50), 31.5 mIU/ml) activity. The sensitivity of the bioassay was less than 0.6 mIU/well. Postmenopausal serum, rat, ovine and bovine FSH elicited a dose-dependent increase in luciferase activity. There was no significant stimulation by highly purified human LH or recombinant human TSH. This cell line should be useful in the determination of bioactive FSH and characterization of serum FSH inhibitors.