Cholecystokinin modulates isoproterenol induced changes in rat parotid gland

1. Parotid gland secretory function and activity of several enzymes involved in intracellular second messenger signalling were measured in rats receiving 0.5 ml i.p. injections of saline (control), isoproterenol, CCK or both drugs. 2. Isoproterenol caused a 2.5-fold increase in parotid gland wet weight compared to control. Chronic administration of CCK alone has no effect on gland weight. A combination of CCK and isoproterenol did not alter the hypertrophy of the gland observed with isoproterenol alone. 3. Isoproterenol administration caused a 74% decrease in parotid gland amylase enzyme activity. While CCK alone did not influence the enzyme activity, it depressed amylase mRNA steady state levels and had an additive effect on further decreasing mRNA levels when administered in combination with beta-agonist. 4. Phospholipase C registered an increase ranging from 22 to 38% in all experimental groups as compared to control. 5. Parotid gland protein kinase C and PdtIns 3-kinase activity were not altered in response to CCK alone, but in combination with isoproterenol, appeared to moderate beta-agonist signal transduction responses.