8] cAMP export and its regulation by prostaglandin A1

Abstract

This chapter examines cAMP export and its regulation by prostaglandin A1. The main requirement for studying export is a method for the rapid separation of the intracellular and extracellular spaces, with collection of both, if possible. Export of cAMP is remarkably sensitive to temperature, occurring only slightly, if at all, below 22° in avian red cells and greatly inhibited by decreased temperatures in S49 lymphoma cells and mammalian reticulocytes. Thus, one may “freeze” the level of exported cAMP by the simple expedient of cooling or by dilution with cold buffer, a handy maneuver in many experimental protocols. Despite the simplicity of these comments and procedures and the relative ease of demonstrating efflux of cellular cAMP, readers should realize that the study of solute export is not subject to rigorous analysis because the exact intracellular activity or concentration of the solute being transported is not known or readily controlled. The export of cAMP seems limited by the cell's ability to produce and accumulate the solute and properties such as saturability are not directly demonstrable.