MELATONIN BINDING-SITES IN THE HARDERIAN-GLAND OF SYRIAN-HAMSTERS - SEXUAL DIFFERENCES AND EFFECT OF CASTRATION

The presence of specific melatonin binding sites in the Harderian gland of Syrian hamsters was studied using [I-125] melatonin. Saturation binding experiments conducted with [I-125] melatonin at 37-degrees-C using Harderian glands of both male and female Syrian hamsters revealed a single nanomolar-affinity site. The dissociation constants (Kd) were 6.47 and 6.94 nM for males and females, respectively. The concentration of the binding sites was 7.58 fmol/mg protein for males and 13.50 fmol/mg protein for females. Castration of male hamsters resulted in a significant increase in [I-125] melatonin binding sites while chronic melatonin administration did not modify the binding properties. The results confirm the presence of melatonin binding sites in the Harderian glands of rodents. The gender-associated differences found together with the effects of castration in male hamsters suggest an androgenic control in [I-125] melatonin binding sites of the Syrian hamster Harderian gland.