Differential processing of subunits of human chorionic gonadotropin by granulosa cells in vivo.

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Abstract
The question of whether the 2 subunits of the glycoprotein hormone human chorionic gonadotropin (hCG) are handled separately or as a unit by target cells was addressed by using a dual-labeling procedure. The individual .alpha. and .beta. subunits of hCG were labeled with 131I or 125I, recombined, chromatographed and injected i.v. into hormonally primed immature rats. The ovaries of these rats contained large numbers of antral follicles, the granulosa cells of which possess high concentrations of receptor for hCG. Comparisons of the distribution of the different radioisotopic labels in various tissues over time indicated the activity associated with the .beta. subunit was preferentially retained by the ovarian granulosa cells in a hormone-specific manner, while the activity associated with the .alpha. subunit was preferentially lost. This contrasted with other tissues, including other ovarian cells with receptor for hCG, in which both radiolabels were either handled nondifferentially or handled differentially in a hormonally nonspecific manner.