Katuhide Tanaka

Calcitonin receptor binding properties in bone and kidney of the chicken during the oviposition cycle.

The binding property of calcitonin (CT) in the membrane fraction of calvaria and kidney of egg‐laying and nonlaying hens was analyzed using a [125I]CT binding assay system. Binding properties of CT receptors in both tissues satisfy the authentic criteria of a receptor‐ligand interaction in terms of specificity, reversibility, and saturation. Scatchard plots revealed a single class of binding sites. Values of the equilibrium dissociation constant (Kd) and binding capacity (Bmax) in laying hens showed a decrease during the period between 3 h before and 2 h after oviposition. No change was observed in nonlaying hens. In vivo administration of 17β‐estradiol or progesterone caused the decrease in Kd and Bmax values. The results suggest that the binding affinity and capacity of the CT receptor in the calvaria and the kidney of the hen may be modulated by the ovarian steroid hormone.

A Vasoactive Intestinal Peptide Binding Component in Hen Granulosa Cells

Abstract In radioligand assays, the vasoactive intestinal peptide (VIP) binding component in the membrane fraction of granulosa cells of the ovary of the hen was shown to possess characteristic properties of a receptor, such as reversible binding, binding specificity, high-affinity, and limited capacity. The binding site was of a single class. The binding affinity was higher in the largest (F1) and the second largest follicle (F2) than in the third largest follicle (F3), and the binding capacity was greater in F2 and F3 than in F1. During the ovulatory cycle, changes in affinity and capacity were observed only in F1 shortly before ovulation. The results suggest the presence of VIP receptor in the hen granulosa cells and its binding is assumed to be related to the follicular growth and ovulation.