Renotropic and gonadotropic activity in homologous and heterologous hybrids of ovine luteinizing hormone and human chorionic gonadotropin subunits.

Abstract

We previously demonstrated the renotropic activity of ovine and porcine LH, i.e. the stimulation of [3H]thymidine incorporation into the renal DNA of castrated hypophysectomized rats. We conducted this study to determine which condition is required to promote renotropic activity. We prepared homologous (oLH alpha.oLH beta, hCG alpha.hCG beta) and heterologous (oLH alpha.hCG beta, hCG alpha.oLH beta) hybrids from isolated oLH- and/or hCG-derived subunits. Native oLH and all hybrids showed gonadotropic activity when examined for cyclic AMP generation in cultured Leydig tumour cells (MA-10). Native oLH and the hybrids which showed renotropic activity were all found to contain at least one of the oLH subunits. Our findings point out the important, special role of oLH subunits in promoting renotropic activity. The condition required is suggested to be presence of a common structure in the two oLH subunits. Such a structure should consequently not be present in hCG. A carbohydrate moiety of oLH containing a sulphate group is proposed as a candidate, but the assumption remains to be demonstrated.