The biological properties of deglycosylated human chorionic gonadotropin (DhCG), obtained by hydrogen fluoride treatment (HF-DhCG) of intact hCG or by oligonucleotide-directed mutagenesis (CHO-DhCG), and that of their fully glycosylated counterparts, were tested in terms of cAMP and steroid production in rat Leydig cells and in mouse Leydig tumor cells (MA-10 cells). In both cell types, HF-DhCG and CHO-DhCG possessed comparable biological activities. The maximum for DhCG-induced cAMP production was approximately 12% of that of intact hCG when tested in rat Leydig cells, and only 2% when tested in MA-10 cells. DhCG possessed significant steroidogenic activity in both cell types. In MA-10 cells the maximum for DhCG-induced steroidogenesis was 30-50% of that of intact hCG, while in rat Leydig cells DhCG and hCG induced similar steroidogenic maxima. Based on its ED50, DhCG possessed 10-17% of the steroidogenic potency of intact hCG in rat Leydig cells, while in MA-10 cells DhCG was only 2-fold less potent than hCG. When accurate hormone-receptor binding data are absent, the intrinsic receptor-stimulating activity of a ligand can still be estimated at full receptor occupancy, provided that over the whole dose range the biological response is proportional to receptor stimulation. The present data show that in transfected MA-10(P+29) cells which over-express rat phosphodiesterase, the hormone-induced stimulation of cAMP and steroid production is directly coupled to receptor activation up to maximal occupation of the LH/CG receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

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Human chorionic gonadotropin (hCG) preparations with different biological activities were tested for their inhibitory effects on mitogenic of allogenic induced lymphocyte response. Various crude hormone batches inhibited the lymphocyte reaction in a dose-dependent manner. However, we found a varying suppression of lymphocyte response not correlated to the biological activity (2,660–4,300 IU/mg) of crude hormone. Fractions with very low gonadotropic activity ( < < 500 IU/mg) showed a 100-fold inhibition of lymphocyte reaction. Conversely, the enrichment of highly purified hCG with strong biological activity ( > 10,000 IU/mg) had no inhibitory effect on mitogenic or allogenic induced lymphocyte transformation. I soelectro focussing and immunoelectrophoretic investigations indicated that the inhibition is probably caused by nondialyzable sialoglyco-proteins. It is therefore very doubtful whether hCG plays an important part in maternal tolerance of the fetal allograft.

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