Effect of estradiol-17β on calcitonin receptor bindings in the hen neurohypophysis

ABSTRACT The present study was performed to elucidate whether estradiol-17β (E2) would affect calcitonin (CT) receptor binding in the hen neurohypophysis. The equilibrium dissociation constant (Kd) and the maximum binding capacity (Bmax) of the CT receptor in the plasma membrane fraction of the hen neurohypophysis were examined by Scatchard analysis of specific binding of 125 I-labeled chicken CT. A single i.m. injection of E2 into nonlaying hens caused a decrease in Kd and Bmax values of the CT receptor. The Kd and Bmax values of the CT receptor were smaller in laying hens than in nonlaying hens. The present study suggests that E2 may increase the action of CT on the neurohypophysis in hens.