Exposure of latent prostaglandin-binding sites in the rat epididymal adipocyte membrane.

The addition of albumin to a suspension of plasma membranes isolated from rat epididymal fat cells increases both the initial binding rate and the maximal specific binding of prostaglandin E2 to these membranes. The presence of albumin affects neither the dissociation rate of bound prostaglandin E2 nor its dissociation constant. The results indicate that the interaction of albumin with the isolated membranes exposes latent prostaglandin-binding sites. Albumin fails to alter the specific binding of prostaglandin E2 to membranes isolated from frog erythrocytes or from rat peritoneal fat cells. These results indicate that the effect of albumin on the specific binding of prostaglandin E2 characterizes a specific molecular property of the prostaglandin receptors in rat epididymal adipocytes.