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The Journal of Neuroscience, April 15, 2001, 21(8):2640-2650

Contribution of the Plasmalemma to Ca²⁺ Homeostasis in Hair Cells

Catherine Boyer^{1, 2}, Jonathan J. Art², Claude J. Dechesne¹, Jacques Lehouelleur¹, Jean Vautrin¹, and Alain Sans¹

¹ Institut National de la Santé et de la Recherche Médicale U-432, Université Montpellier II, 34095 Montpellier cedex 05, France, and ² University of Illinois, College of Medicine, Department of Anatomy and Cell Biology, Chicago, Illinois 60612

Calcium influx through transduction channels and efflux via plasmalemmal Ca²⁺-ATPases (PMCAs) are known to contribute to calcium homeostasis and modulate sensory transduction in vertebrate hair cells. To examine the relative contributions of apical and basolateral pathways, we analyzed the calcium dynamics in solitary ciliated and deciliated guinea pig type I and type II vestibular hair cells. Whole-cell patch-clamp recordings demonstrated that these cells had resting potentials near 70 mV and could be depolarized by 10-20 mV by superfusion with high potassium. Fura-2 measurements indicated that ciliated type II cells and deciliated cells of either type had low basal [Ca²⁺]_i, near ~90 nM, and superfusion with high potassium led to transient calcium increases that were diminished in the presence of Ca²⁺ channel blockers. In contrast, measurements of type I ciliated cells, hair cells with large calyceal afferents, were associated with a higher basal [Ca²⁺]_i of ~170 nM. High-potassium superfusion of these cells induced a paradoxical decrease in [Ca²⁺]_i that was augmented in the presence of Ca²⁺ channel blockers. Optical localization of dihydropyridine binding to the kinocilium suggests that they contain L-type calcium channels, and as a result apical calcium influx includes a contribution from voltage-dependent ion channels in addition to entry via transduction channels localized to the stereocilia. Eosin block of PMCA significantly altered both [Ca²⁺]_i baseline and transient responses only in ciliated cells suggesting that, in agreement with immunohistochemical studies, PMCA is primarily localized to the bundles.

Key words: PMCA; calcium channels; vestibular hair cells; bundles; fura-2 fluorescence; guinea pig

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Copyright © 2001 Society for Neuroscience  0270-6474/01/2182640-11$05.00/0

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				J. K. Hill, C. L. Brett, A. Chyou, L. M. Kallay, M. Sakaguchi, R. Rao, and P. G. Gillespie Vestibular Hair Bundles Control pH with (Na+, K+)/H+ Exchangers NHE6 and NHE9 J. Neurosci., September 27, 2006; 26(39): 9944 - 9955. [Abstract] [Full Text] [PDF]

				S. S. Desai, C. Zeh, and A. Lysakowski Comparative Morphology of Rodent Vestibular Periphery. I. Saccular and Utricular Maculae J Neurophysiol, January 1, 2005; 93(1): 251 - 266. [Abstract] [Full Text] [PDF]

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