Agonist-induced Ca2+ mobilization in the rat submandibular gland during aging and subsequent to chronic propranolol treatment.
The effects of age and chronic propranolol treatment on the agonist-induced rise in intracellular free Ca2+ ([Ca2+]i), an index for the coupling of receptor-second messenger generation, was studied using a dispersed rat submandibular gland preparation. Muscarinic stimulation (10 microns carbachol) caused a rapid (T1/2 less than 2 s) and dramatic (approximately 4.5-fold) rise in [Ca2+]i followed by a lower sustained increase (approximately 3-fold) in [Ca2+]i as measured directly with the Ca(2+)-sensitive fluorescent probe, fura-2. The magnitude and the rate of increase of the initial rise in [Ca2+]i and the level of the sustained increase in [Ca2+]i were not different between 2- an 21-month-old rats. Stimulation in a Ca(2+)-free medium reduced the initial agonist-induced increase in [Ca2+]i by approximately 35-40%, while the sustained increase was abolished by the removal of extracellular Ca2+ from cells in both young and old rats. Chronic treatment for 30 days with 20 mg/kg propranolol, a beta-adrenergic antagonist, did not significantly alter the ability of dispersed submandibular cells in old rats to mobilize Ca2+ during agonist stimulation or influence the in vivo stimulated gland output. These results suggest that the agonist-induced rise in [Ca2+]i is not altered by aging or by chronic treatment of aged rats with propranolol and, therefore, receptor-second messenger coupling remains intact.
Melvin
J E
JE
Department of Dental Research, University of Rochester, NY 14642.
O'Connell
A C
AC
Koek
L
L
Bowen
W H
WH
D000375:Aging / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D007545:Isoproterenol / Q000494:pharmacology; D010862:Pilocarpine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013363:Submandibular Gland / Q000187:drug effects / Q000378:metabolism*
D010862:Pilocarpine; D002217:Carbachol; D011433:Propranolol; D007545:Isoproterenol; D002118:Calcium