Ability of human chorionic gonadotropin β-subunit to inhibit the steroidogenic response to lutropin

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Abstract
Ability of the .beta.-subunit of human chorionic gonadotropin [hCG] to inhibit the response to lutropin (luteinizing hormone, LH) was tested in the immature rat ovarian system and pregnant-mare-serum-gonadotropin-primed rat ovarian system with progesterone [P] production being used as the response. hCG .beta.-subunit inhibited human and ovine LH-stimulated P production. At a constant dose of LH, inhibition was dependent on the concentration of .beta.-subunit. When concentration of the .beta.-subunit was kept constant at 5.0 .mu.g/ml and the concentration of LH was varied, the inhibition was maximum at the saturating concentration of the native hormone. The .alpha.-subunit of the hCG did not inhibit the response to LH. The LH/.beta.-subunit ratio required to produce an inhibition of response was much lower than that required to bring about an observable inhibition of binding.