Comparison of agonist-induced Ca2+ responses in rat submandibular acini and ducts.
Changes in intracellular Ca(2+) concentration ([Ca(2+)]i) induced by agonists were simultaneously monitored in rat submandibular acini and ducts using a Ca(2+) imaging system. Substance P (SP) elicited marked increases in [Ca(2+)]i in acini but not in ducts. Carbachol (CCh) increased [Ca(2+)]i in both acini and ducts, but the maximal level was higher in acini than in ducts. In contrast, epinephrine (Epi) also induced an increase in [Ca(2+)]i in acini and ducts, but to a greater extent in ducts than in acini. Isoproterenol (ISO) caused a small but significant increase in [Ca(2+)]i in ducts but not acini. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis using total RNA extracted from highly purified acinar and ductal cells showed that substance P receptor mRNA was present in acini at higher levels than in ducts. In contrast, alpha(1a)-adrenoceptor mRNA was more strongly expressed in ducts than in acini. The muscarinic receptors (M(3) and M(5)) and beta-adrenoceptors (beta(1) and beta(2)) were expressed at equivalent levels in both cell types. These results confirm that acini and ducts exhibit significant differences in agonist-induced Ca(2+) responses. Furthermore, substance P- and epinephrine-induced Ca(2+) responses were consistent with receptor mRNA expression in acini and ducts, but carbachol- and isoproterenol-induced [Ca(2+)]i increases were not.
Nezu
Akihiro
A
Department of Dental Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido 061-0293, Japan. a-nezu@hoku-iryo-u.ac.jp
Morita
Takao
T
Tanimura
Akihiko
A
Tojyo
Yosuke
Y
D000818:Animals; D002118:Calcium / Q000819:agonists / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D016257:Fura-2; D007424:Intracellular Fluid / Q000187:drug effects* / Q000378:metabolism; D007477:Ions; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008856:Microscopy, Fluorescence; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D011943:Receptors, Adrenergic, beta / Q000235:genetics; D011976:Receptors, Muscarinic / Q000235:genetics; D018040:Receptors, Neurokinin-1 / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013268:Stimulation, Chemical; D013363:Submandibular Gland / Q000187:drug effects* / Q000378:metabolism; D013373:Substance P / Q000494:pharmacology
D007477:Ions; D012333:RNA, Messenger; D011943:Receptors, Adrenergic, beta; D011976:Receptors, Muscarinic; D018040:Receptors, Neurokinin-1; D013373:Substance P; D002217:Carbachol; D007545:Isoproterenol; D002118:Calcium; D016257:Fura-2; D004837:Epinephrine