BINDING OF HUMAN CHORIONIC GONADOTROPHIN BY RAT TESTIS: EFFECT OF SEXUAL MATURATION, CRYPTORCHIDISM AND HYPOPHYSECTOMY

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Abstract
The specific binding of 125I-labelled human chorionic gonadotrophin (HCG) by rat testicular homogenate as compared with isolated Leydig cells differs with respect to total binding capacity but not to the dissociation constant (KD) as revealed by Scatchard analysis. The maximal binding capacity for [125I]HCG of crude testicular homogenate was 95 ng/g rat testis. Hypophysectomy causes a decline in binding capacity within the first three days but on the 20th and 30th day after hypophysectomy the relative binding capacity no longer differs from that of controls. Binding capacity is enhanced in cryptorchid testes relative to normal, and increases during sexual maturation to a peak shortly before puberty.