Comparative Analysis of Rat Uterine Estrogen-Induced Creatine Kinase With Monoclonal Antibodies

Monoclonal antibodies were generated against rat uterine estrogen-induced protein--creatine kinase (CK-EIP)--and two (MAb-28 and MAb-78) were studied. These antibodies were IgM but differed in their complementary antigenic determinants both of which were detectable on denatured but not on native CK-EIP. MAb-28 reacted with other CK-BBs but not with CK-MMs whereas MAb-78 reacted with both types of CKs. A measurement of antigenicity with the monoclonal antibodies under calibrated conditions showed differences among the CKs, notably between CK-BB from rat brain and CK-EIP when both were probed with MAb-28. The antigenicity of CK-BB (rat brain) was significantly lower than that of CK-EIP, indicating that the former either expresses less copies of the determinant recognized by MAb-28 than CK-EIP does, or possesses a determinant which interacts with the antibody with lower affinity. The monoclonal antibodies should help elucidate structure-function relationships in CK-BB and CK-EIP molecules, their anatomic distribution and their physiologic, pathologic and experimental variations in relation to gene expression induced by sex hormones.