title: α1-Adrenoceptors relate Ca(2+) modulation and protein secretions in rat lacrimal gland.
abstract: Noradrenaline (NA) is a catecholamine with multiple roles including as a hormone and a neurotransmitter. Cellular secretory activities are enhanced by adrenergic stimuli as well as by cholinergic stimuli. The present study aimed to determine which adrenoceptors play a role in controlling intracellular calcium ion ([Ca(2+)]i) level in acinar cells of rat lacrimal glands. Expression of mRNA for adrenoceptor subtypes in the acinar cells was assessed using RT-PCR. All types except α2c, β1, and β3 were detected. NA induced a [Ca(2+)]i increase with a biphasic pattern in the acinar cells. Removal of extracellular Ca(2+) and use of Ca(2+)-channel blockers did not inhibit the NA-induced [Ca(2+)]i increases. In contrast, U73122 and suramin almost blocked these increases. The α1-adrenoceptor agonist phenylephrine induced a strong increase in [Ca(2+)]i. However, clonidine and isoproterenol failed to induce a [Ca(2+)]i increase. The peroxidase activity was quantified as a measure of mucin secretion. Ca(2+)-dependent exocytotic secretion of peroxidase was detected in rat lacrimal glands. The RT-PCR results showed that MUC1, MUC4, MUC5AC, MUC5B, and MUC16 were expressed in acinar cells. These findings indicated that NA activates α1-adrenoceptors, which were found to be the main receptors in Ca(2+)-related cell homeostasis and protein (including mucin) secretion in lacrimal glands.
authors.affiliation: Department of Anatomy (Cell Biology), Iwate Medical University.
authors.forename: Chika
authors.initials: C
authors.lastname: Ikeda-Kurosawa
authors.forename: Hironori
authors.initials: H
authors.lastname: Higashio
authors.forename: Masato
authors.initials: M
authors.lastname: Nakano
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Okubo
authors.forename: Yoh-Ichi
authors.initials: Y
authors.lastname: Satoh
authors.forename: Daijiro
authors.initials: D
authors.lastname: Kurosaka
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Saino
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D003000:Clonidine / Q000494:pharmacology; D006706:Homeostasis; D007091:Image Processing, Computer-Assisted; D007545:Isoproterenol / Q000494:pharmacology; D007765:Lacrimal Apparatus / Q000166:cytology / Q000378:metabolism*; D008297:Male; D009077:Mucins / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D009195:Peroxidase / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D018340:Receptors, Adrenergic, alpha-1 / Q000235:genetics / Q000378:metabolism*
chemical_list: D009077:Mucins; D012333:RNA, Messenger; D018340:Receptors, Adrenergic, alpha-1; D009195:Peroxidase; D007545:Isoproterenol; D003000:Clonidine; D002118:Calcium; D009638:Norepinephrine