title: Cellular mechanism of adrenalin stimulated chloride secretion via beta-adrenoceptor in T84 cells.
abstract: In the present study, the intracellular regulatory pathways involved in the adrenalin-stimulated chloride secretion across T84 cells were investigated. Biphasic characteristics were observed in the Isc response to the basolateral addition of adrenalin (0.25 nM-100 microM). The biphasic response was almost abolished by removing ambient Cl(-). Chloride secretion was found to depend on the activities of basolaterally located Na+-K+-2Cl(-) cotransporters and K+ channels. The alpha-adrenoceptor antagonist phentolamine did not have any effect on either phase of adrenalin-induced Isc, while after pretreatment of the beta-adrenoceptor antagonist propranolol, the adrenalin-induced Isc was substantially abolished, suggesting the biphasic response may be mediated by the beta-adrenoceptor. Under whole cell patch-clamp conditions, T84 cells responded to adrenalin with a rise in inward current. The current, which exhibited a linear I-V relationship and time- and voltage-independent characteristics, was inhibited by the chloride channel blocker DPC and the reverse potential was close to the equilibrium potential for Cl(-) (0 mV), implying that the current was Cl(-) selective. When preloaded with a Ca2+-chelating agent, BAPTA/AM did not affect the Isc response to adrenalin, whereas the Isc was destroyed by pretreating the cells with an adenyl cyclase inhibitor, MDL12330A. These observations were further supported by the intracellular [cAMP] measurement experiment, indicating that adrenalin induced chloride secretion could be mediated by a beta-adrenoceptor only involving cAMP as an intracellular second messenger.
authors.affiliation: School of Life Science, Sun Yat-Sen University, 135 Xingang West Road, Guangzhou 510275, PR China.
authors.forename: Zi-Huan
authors.initials: ZH
authors.lastname: Yang
authors.forename: Ao
authors.initials: A
authors.lastname: Pan
authors.forename: Ye-Chun
authors.initials: YC
authors.lastname: Ruan
authors.forename: Hai-Jie
authors.initials: HJ
authors.lastname: Yu
authors.forename: Zhong-Luan
authors.initials: ZL
authors.lastname: Wu
authors.forename: Hui
authors.initials: H
authors.lastname: Xiang
authors.forename: Wen-Liang
authors.initials: WL
authors.lastname: Zhou
mesh_terms: D018674:Adrenergic Antagonists / Q000494:pharmacology; D045744:Cell Line, Tumor; D018118:Chloride Channels / Q000037:antagonists & inhibitors; D002712:Chlorides / Q000378:metabolism*; D003106:Colon / Q000166:cytology / Q000502:physiology; D000242:Cyclic AMP / Q000378:metabolism; D004553:Electric Conductivity; D004837:Epinephrine / Q000494:pharmacology*; D006801:Humans; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D017136:Ion Transport; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000378:metabolism; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*
chemical_list: D018674:Adrenergic Antagonists; D018118:Chloride Channels; D002712:Chlorides; D015221:Potassium Channels; D011943:Receptors, Adrenergic, beta; D000242:Cyclic AMP; D004837:Epinephrine