RECOMBINANT THYROTROPIN STIMULATES CAMP FORMATION IN CHO-K1 CELLS EXPRESSING RECOMBINANT CHORIONIC-GONADOTROPIN RECEPTOR

Using CHO-K1 cells expressing rat thyrotropin-receptor (CHO-rTSH-R cells) or rat chorionic gonadotropin-receptor (CHO-rCG-R cells), we have examined their reactivity or cross-reactivity to recombinant human thyrotropin (TSH) or human chorionic gonadotropin (hCG). TSH stimulated cAMP formation in CHO-rTSH-R cells dose-dependently, and the maximum response was obtained at 1 mIU/ml. hCG also increased cAMP in the cells from 104 mIU/ml, and the maximum stimulation was observed at 106 mIU/ml. 107 mIU of hCG had the same potency with 1 mIU of TSH to rTSH-R. On the other hand, 10-1 mIU/ml of hCG increased cAMP content in CHO-rCG-R cells and reached the maximum level at 102 mIU/ml. TSH also showed the stimulatory activity to CHO-rCG-R cells. It increased cAMP formation in CHO-rCG-R cells dose-dependently from 10 mIU/ml to 103 mIU/ml. Thirty mIU of TSH was calculated to be equivalent to 1 mIU of hCG to CG-R. These results indicate that TSH and hCG cross-react each other with rTSH-R or rCG-R. © 1993 Academic Press, Inc.