DEGRANULATION OF RAT SALIVARY-GLANDS FOLLOWING TREATMENT WITH RECEPTOR-SELECTIVE AGONISTS

1. The aim of this study was to find a drug that induces an almost com plete degranulation of secretory cells in rat parotid and submandibula r glands. 2. Phenylephrine (alpha-adrenergic), isoproterenol (beta-adr energic) and mecholine (muscarinic cholinergic) were tested. Time and degree of maximal depletion of acinar and granular convoluted tubule c ells were determined morphologically. 3. Following phenylephrine-injec tion (5 mg/kg or 10.2 mg/kg, i.p.), no effect on the acinar granulatio n level was observed in either of the glands, while about 50-60% granu lar convoluted tubules were degranulated for at least 120-180 min post injection. 4. With isoproterenol (5, 10, 40, 70 or 100 mg/kg, i.p.), d egranulation of 100% of the acinar cells in the parotid and 80% of the acinar cells in the submandibular gland was observed 90 min post-inje ction. Granular convoluted tubule cells did not respond to this beta-a drenergic drug. 5. Mecholine (3.75 or 7.5 mg/kg, i.p.) induced mainly degranulation of granular convoluted tubule cells (about 50% after 120 min). Numbers of granulated acinar cells decreased only slightly in b oth glands (about 10%, 90-120 min). 6. From this study it appears that with a relatively low dosage (5 mg/kg, i.p.) of isoproterenol, a high level of degranulation can be induced in acinar cells of rat parotid and submandibular glands without toxic side effects. Concerning granul ar convoluted tubules, only moderate degranulation was observed with p henylephrine and mecholine, respectively.