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

Abstract

Ability of the β-subunit of human chorionic gonadotropin 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 production being used as the response. Human chorionic gonadotropin β-subunit was found to inhibit human and ovine lutropin-stimulated progesterone production. At a constant dose of lutropin, inhibition was dependent on the concentration of β-subunit. When concentration of the β-subunit was kept constant at 5.0 μg/ml and the concentration of lutropin was varied, the inhibition was maximum at the saturating concentration of the native hormone. The α-subunit of the human chorionic gonadotropin did not inhibit the response to lutropin. The lutropin/β-subunit ratio required to produce an inhibition of response was much lower than that required to bring about an observable inhibition of binding.