Introduction of cyclic AMP phosphodiesterase into rat submandibular acini prevents isoproterenol-stimulated cyclic AMP rise without affecting mucin secretion.

Cyclic AMP phosphodiesterase has been incorporated into isolated rat submandibular acini by hypotonic swelling. This resulted in complete inhibition of the cyclic AMP rise stimulated by isoproterenol (10 microM), but had no effect on the stimulation of mucin secretion. Acini swollen in the absence of cyclic AMP phosphodiesterase showed similar cyclic AMP and mucin secretion responses to those of unswollen acini. The dissociation between cyclic AMP rise and mucin secretion was not due to stimulation of different beta-receptor subtypes since both responses to isoproterenol were inhibited by the beta 1 antagonist atenolol, but not by the beta 2 antagonist, butoxamine. The results are the first to directly demonstrate that a maximally effective concentration of isoproterenol can increase mucin secretion in the absence of a detectable increase in cyclic AMP.