Residual secretion of amylase induced by isoproterenol from rat parotid gland slices.

1. During pretreatment with isoproterenol (ISP) for 2 min the accumulation of cyclic AMP increased in a dose-dependent manner but amylase release did not increase even in the highest dose of ISP used. 2. After a brief pretreatment with ISP, the following 10-min incubations with fresh medium without ISP caused increase in amylase secretion (residual secretion). However, cyclic AMP accumulation returned to the non-treated level during the residual secretion of amylase. 3. Both residual amylase release and cyclic AMP accumulation after pretreatment with ISP were enhanced in the presence of isobutyl-methylxanthine. Residual amylase release was not affected in the absence of extracellular calcium ion. 4. We suggest that there may be another pathway than cyclic AMP to cause residual amylase secretion induced by brief pretreatment with ISP in rat parotid acinar cells.