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.