Methods for the Study of Cyclic AMP Metabolism in Intact Cells

Abstract

The concentration of adenosine 3′:5′-monophosphate (cAMP) in cells is determined predominantly by the relative rates of synthesis by adenylate cyclase and degradation by phosphodiesterase; although other contributing factors may exist. For example, a significant portion of the cAMP content under basal conditions may exist in a protein-bound form that is not susceptible to hydrolysis by phosphodiesterase activity (1). Also, in certain cases the rate of secretion of cAMP from hormonally-stimulated cells can be a major factor in determining the intracellular content (2, 3). It is usually assumed that hormones elicit a rise in cellular cAMP levels by activation of adenylate cyclase. However, if some degree of turnover of cAMP occurs under basal conditions, then theoretically, the steady state level of cAMP could be raised by either an increase in its rate of synthesis or a decrease in its rate of degradation.