EFFECTS OF RECEPTOR AGONISTS ON POLYAMINE CONCENTRATIONS AND SPERMIDINE SPERMINE N(1)-ACETYLTRANSFERASE ACTIVITY IN RAT PAROTID-GLAND

The polyamine putrescine might be formed via a degradation (catalyzed by spermidine/spermine N1-acetyltransferase, SSAT) of the higher polya mines spermidine and spermine to putrescine. The involvement of differ ent intracellular signal pathways in the regulation of putrescine form ation was studied in explants and in cultured cells of rat parotid gla nds by using receptor agonists that activate separate second messenger systems, and measuring their effects on the concentrations of putresc ine, spermidine and spermine and on the SSAT activity. The beta-adreno ceptor agonist isoprenaline, which is an activator of cAMP formation, increased the putrescine concentration and stimulated the SSAT activit y. Pilocarpine, a drug that activates the muscarinic receptors and the reby enhances the phosphoinositide turnover, had no effect on either t he polyamine concentrations or on the SSAT activity. Epidermal growth factor (EGF), which induces activation of a protein tyrosine kinase, h ad no effect on the polyamine concentrations or on the SSAT activity. The adenylate cyclase activator forskolin increased the glandular leve ls of putrescine. Taken together, these findings suggest that increase s in putrescine concentration in cultured rat parotid gland cells are accompanied by accumulation of cAMP.