Gramicidin-perforated patch analysis on HCO3- secretion through a forskolin-activated anion channel in rat parotid intralobular duct cells

Citation
C. Hirono et al., Gramicidin-perforated patch analysis on HCO3- secretion through a forskolin-activated anion channel in rat parotid intralobular duct cells, J MEMBR BIO, 180(1), 2001, pp. 11-19
Citations number
33
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Cell & Developmental Biology
Journal title
JOURNAL OF MEMBRANE BIOLOGY
ISSN journal
0022-2631 → ACNP
Volume
180
Issue
1
Year of publication
2001
Pages
11 - 19
Database
ISI
SICI code
0022-2631(20010301)180:1<11:GPAOHS>2.0.ZU;2-I
Abstract
Forskolin-induced anion currents and depolarization were investigated to cl arify the mechanism of HCO3- secretion in the intralobular duct cells of ra t parotid glands. Anion currents of the cells were measured at the equilibr ium potential of K+, using a gramicidin-perforated patch technique that neg ligibly affects intracellular anion concentration. The forskolin-induced an ion current was sustained and significantly (54%) suppressed by glibenclami de (200 muM), a blocker of the cystic fibrosis transmembrane conductance re gulator (CFTR) Cl- channel. The anion current was markedly suppressed by ad dition of 1 mM methazolamide, a carbonic anhydrase inhibitor, and removal o f external HCO3-. Forskolin depolarized the cells in the current-clamp mode . Addition of methazolamide and removal of external HCO3- significantly dec reased the depolarizing level. These results suggest that activation of ani on channels (mainly the CFTR Cl- channel located in luminal membranes) and production of cytosolic HCO3- induce the inward anion current and resulting depolarization. Inhibition of the Na+-K+-2Cl(-) cotransporter and the Cl-- HCO3- exchanger had no significant effect on the current or depolarization, indicating that the uptake of Cl- via the Na+-K+-2Cl(-) cotransporter or t he Cl--HCO3- exchanger is not involved in the responses. Taken together, we conclude that forskolin activates the outward movement (probably secretion ) of HCO3- produced intracellularly, but not of Cl- due to lack of active C l- transport in parotid duct cells, and that the gramicidin-perforated patc h method is very useful to analyze anion transport.