Polymorphism of human pituitary lutropin (LH). Effect of the seven isohormones on mouse Leydig cell functions

The effect of the 7 different molecular forms of human pituitary lutropin (LH) on mouse Leydig cells as a model of a target organ were studied. The hormone functions have been characterized by receptor binding, cAMP accumulation and testosterone production. One important finding was the similar intrinsic in vitro biological activity for all isohormones. Quantitatively, however, the potencies of the 7 hormone forms did not correlate with the activities obtained by radioimmunoassay: there was a dramatic decrease of receptor binding activity and biological activity compared to immunoactivity from the more alkaline to the more acidic LH isohormones.