The duality of fish gonadotropin receptors: cloning and functional characterization of a second gonadotropin receptor cDNA expressed in the ovary and testis of amago salmon (Oncorhynchus rhodurus).

We previously isolated a cDNA encoding a gonadotropin receptor (sGTH-R) from amago salmon (Oncorhynchus rhodurus) ovarian follicles. In the present study, we cloned a second gonadotropin receptor (sGTH-RI) from the same RNA preparations. Overall sequence homology between sGTH-RI and sGTH-R is 44%. The highest homology occurs with mammalian FSH receptors (49%). Functional characterization examined in COS-7 cells transiently transfected with sGTH-RI showed the largest increase in cAMP production when exposed to salmon GTH I. These results provide the first evidence in any ectothermic vertebrate, the amago salmon, of the duality of gonadotropin receptors. Copyright 1999 Academic Press.