Hirono, Chikara

Iwasa, Yoshiko

Shiba, Yoshiki

Sugita, Makoto

Tokushima University Institutional Repository

To clarify difference of anion secretory functionbetween acinar and intralobular duct cells in the ratparotid gland, we investigated anion currents withthe gramicidin-perforated patch recording method.Anions are supplied only by the cells themselves andreleased through anion channels in the gramicidin-perforated patch configuration. Accordingly, the an-ion currents measured with the present method re-flect the anion-supplying activity and the anion chan-nel activity of the cells (1). Furthermore, anion con-ductance, which reflects the anion channel activity,can be measured by superimposition of brief 5 mVpulses on the holding potential separately from an-ion currents. Thereafter the driving force, which re-flects intracellular anion concentration, can be esti-mated.In the acinar cells, carbachol (CCh), a Ca2+-increasing agent, induced an oscillatory anion cur-rent, of which amplitude became rather steady in5 min after the CCh addition. cAMP- increasingagents, isoproterenol (IPR) and forskolin, evokedno marked current and reduced the CCh-inducedoscillatory current (2). Bumetanide suppressed theCCh-induced oscillatory current in the steady state,suggesting that the oscillatory current in the steadystate is driven mainly by Cl-- uptake activity of theNa+-K+-2Cl-- cotransporter. Superimposition of brief5 mV pulses on the holding potential, --80 mV, underthe suppression of K+ channels by blockers revealedthat anion conductance was oscillatory. The Ca2+ionophore, A23187, induced a nonoscillatory inwardcurrent in the acinar cells. The A23187-induced cur-rent and the driving force in the steady state werebumetanide-sensitive, but membrane conductancewas not very sensitive to bumetanide. These areconsistent with the effect of bumetanide on the CCh-induced oscillatory current.In the intralobular duct cells, both CCh and IPRinduced nonoscillatory currents with nonoscilla-tory increases in membrane conductance. The Ca2+ionophore, A23187, mimicked the CCh-induced cur-rent and the A23187-induced current in the steadystate was blocked by diphenylamine-2-carboxylate.Forskolin mimicked the IPR-induced current andthe forskolin-induced current in the steady state wassensitive to glibenclamide (3) and CFTRinh-172. Allthese currents during the steady state were inhib-ited by HCO3-- removal and addition of methazola-mide and 5-(N,N-dimethyl)amiloride (DMA). Thedriving force, estimated from currents and mem-brane conductance, was sensitive to methazolamideand DMA, but membrane conductance was not.These suggest that the duct cells secrete HCO3-- withcoordinated activities of the carbonic anhydrase andthe Na+-H+ exchanger, through a kind of Ca2+-de-pedent Cl-- channel and the CFTR Cl-- channel acti-vated by Ca2+ and cAMP signals, respectively.We conclude that Cl-- secretion in acinar cells de-pends on an oscillatory increase in anion conduc-tance and the driving force produced by the Na+-K+-2Cl-- cotransporter during the Ca2+ signaling, whileHCO3-- secretion in intralobular duct cells is main-tained by nonoscillatory increases in anion conduc-tance and the driving force generated by the car-bonic anhydrase with the support of the Na+-H+ ex-changer during both Ca2+ signaling and cAMP sig-naling.EXPANDED ABSTRACTAnion secretory functions of acinar and intralobular ductcells in the rat parotid glandChikara Hirono, Makoto Sugita, Yoshiko Iwasa, and Yoshiki ShibaDepartment of Oral Physiology, Hiroshima University Graduate School of Biomedical Sciences,Hiroshima, JapanKeywords : parotid gland, anion secretion, Cl -- channel, Na+-K +-2Cl -- cotransporter, carbonic anhydraseJ. Med. Invest. 56 Suppl. : 299-300, December, 2009Received for publication October 15, 2009 ; accepted October22, 2009.Address correspondence and reprint requests to Chikara Hirono,Department of Oral Physiology, Hiroshima University GraduateSchool of Biomedical Sciences, 2-3, Kasumi 1-Chome, Minami-ku, Hiroshima 734-8553, Japan and Fax : +81-82-257-5627.The Journal of Medical Investigation Vol. 56 Supplement 2009299REFERENCES1. Hirono C, Shiba Y : Analyses of anion secretionby the gramicidin-perforated patch recordingin secretory epithelial cells. Recent Res DevelMembr Biol 1 : 11-21, 20022. Shintani T, Hirono C, Sugita M, Iwasa Y, ShibaY : Suppression of carbachol-induced oscilla-tory Cl-- secretion by forskolin in rat parotid andsubmandibular acinar cells. Am J Physiol Gas-trointest Liver Physiol 294 : G738-G747, 20083. Hirono C, Nakamoto T, Sugita M, Iwasa Y,Akagawa Y, Shiba Y : Gramicidin-perforatedpatch analysis on HCO3-- secretion through aforskolin-activated anion channel in rat parotidintralobular duct cells. J Membr Biol 180 : 11-19, 2001C. Hirono, et al. Anion secretion in rat parotid cells300

Anion secretory functions of acinar and intralobular duct cells in the rat parotid gland

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Anion secretory functions of acinar and intralobular duct cells in the rat parotid gland

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