Mesotocin receptor binding of cortical and medullary kidney tissues of the hen

Department of Animal Science and Technology, Gifu University, Japan.

[125I]Mesotocin (MT) binding of membrane fractions of the cortical tissue and the medullary tissue (medullary cone) of the kidney of nonlaying hens was measured by the use of radioligand binding assays to determine the distribution of two distinct MT receptors within the hen kidney. The binding to [125I]MT in the medullary tissue was found to be highly competitive with unlabeled MT. In the cortical tissue, the binding was competitive with both unlabeled MT and arginine vasotocin. Kinetic and Scatchard analyses of specific binding revealed that the binding affinity was higher in the cortical tissue than in the medullary tissue, but the binding capacity was less in the cortical tissue. The localization of two distinct MT receptor having different binding properties may be related to the biphasic action of MT within the tissue of the kidney of the hen.