CHOLECYSTOKININ MODULATES ISOPROTERENOL-INDUCED CHANGES IN RAT PAROTID-GLAND

1. Parotid gland secretory function and activity of several enzymes in volved in intracellular second messenger signalling were measured in r ats receiving 0.5 ml i.p. injections of saline (control), isoprotereno l, CCK or both drugs. 2. Isoproterenol caused a 2.5-fold increase in p arotid gland wet weight compared to control. Chronic administration of CCK alone has no effect on gland weight. A combination of CCK and iso proterenol did not alter the hypertrophy of the gland observed with is oproterenol alone. 3. Isoproterenol administration caused a 74% decrea se in parotid gland amylase enzyme activity. While CCK alone did not i nfluence the enzyme activity, it depressed amylase mRNA steady state l evels and had an additive effect on further decreasing mRNA levels whe n administered in combination with beta-agonist. 4. Phospholipase C re gistered 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 co mbination with isoproterenol, appeared to moderate beta-agonist signal transduction responses.