Cyclic AMP accumulation in the beta adrenergic mechanism of eccrine sweat secretion

Tissue cyclic 3'5'-AMP (cAMP) concentrations were measured after stimulation of isolated monkey palm eccrine sweat glands with various stimulants of sweat secretion. The cellular cAMP levels increased curvilinearly with time of incubation to reach a steady state after 5 min of incubation with isoproterenol. Theophylline more than doubled the isoproterenol-induced cAMP accumulation, whereas theophylline alone increased the basal cAMP level to a minor extent. Phenylephrine failed to stimulate cAMP accumulation. There was no increase in the cAMP level after stimulation with methacholine. A calcium ionophore, A23187, also failed to stimulate cAMP accumulation. Since isoproterenol, theophylline (or isobutylmethylxanthine), and dibutyryl cAMP all induced eccrine sweat secretion in isolated, cannulated sweat glands to varying degrees in vitro, cAMP is probably involved in the beta adrenergic mechanism of sweat induction. The isoproterenol-induced cAMP accumulation was not inhibited by removal of Ca2+ from the incubation medium for as long as 30 min. The striking similarity between the eccrine sweat gland and the salivary glands in the roles that Ca2+ and cAMP play in stimulus secretion coupling indicates that the eccrine sweat gland will serve as another useful model system for the study of the mechanisms of exocrine secretion.