Effects of intracellular pH and Ca2+ on the activity of stretch-sensitive cation channels in leech neurons

Year: 2006

Authors: Barsanti C., Pellegrini M., Ricci D., Pellegrino M.

Autors Affiliation: Dipartimento di Fisiologia e Biochimica \”G. Moruzzi\”, Università di Pisa, Via S. Zeno 31, 56127, Pisa, Italy; Scuola Normale Superiore, Piazza Cavallieri 7, 56126, Pisa, Italy.

Abstract: The effects of intracellular pH and calcium on the activity of the leech mechanosensitive cation channels have been studied. These channels exhibited two activity modes denoted as spike-like (SL) and multiconductance (MC). In the absence of mechanical stimulation, acidification of the intracellular side of membrane patches from 7.2 to 6.2 reversibly increased the mean channel open time as well as the opening frequency in the SL mode. Channels in MC mode were activated by a pH(i) reduction from 7.2 to 6.2, but were inhibited at pH(i) 5.5. Unlike MC mode, SL mode was strongly activated by intracellular Ca2+. Fura-2 imaging experiments showed that intracellular calcium was induced to increase by hypotonic cell swelling. The major component of this response did not require extracellular calcium. A component of the swelling-induced calcium response was sensitive to blockers of stretch-sensitive cation channels. The results indicate that the two activity modes of mechanosensitive channels of leech neurons respond differently to changes of intracellular pH and calcium. The sensitivity of the channel to micromolar concentrations of internal free calcium, along with its permeability to this ion, is consistent with a role in the amplification of mechanically induced Ca2+ signals in leech neurons.

Journal/Review: PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY

Volume: 452 (4)      Pages from: 435  to: 443

KeyWords: mechanosensitive ion channels; patch clamp; single-channel recording; calcium imaging; TRP channels
DOI: 10.1007/s00424-006-0056-7

Citations: 3
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