The Role of Calcium in the Volume Regulation of Rat Lacrimal Acinar Cells |
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Authors: | T. Speake I.J. Douglas P.D. Brown |
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Affiliation: | (1) Cell Physiology Group, School of Biological Sciences (G.38), University of Manchester, Manchester, M13 9PT, UK, GB |
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Abstract: | Earlier studies have suggested a role for Ca2+ in regulatory volume decrease (RVD) in response to hypotonic stress through the activation of Ca2+-dependent ion channels (Kotera & Brown, 1993; Park et al., 1994). The involvement of Ca2+ in regulating cell volume in rat lacrimal acinar cells was therefore examined using a video-imaging technique to measure cell volume. The trivalent cation Gd3+ inhibited RVD, suggesting that Ca2+ entry is important and may be via stretch-activated cation channels. However, Fura-2 loaded cells did not show an increase in [Ca2+] i during exposure to hypotonic solutions. The absence of any changes in [Ca2+] i resulted from the buffering of cytosolic Ca2+ by Fura-2 during hypotonic shock and therefore inhibition of RVD. The intracellular Ca2+ chelator, BAPTA, also inhibited the RVD response to hypotonic shock. An increase in [Ca2+] i induced by either acetylcholine or ionomycin, was found to decrease cell volume under isotonic conditions in lacrimal acinar cells. Cell shrinkage was inhibited by tetraethylammonium ion, an inhibitor of Ca2+-activated K+ channels. On the basis of the presented data, we suggest an involvement of intracellular Ca2+ in controlling cell volume in lacrimal acinar cells. Received: 20 February 1998/Revised: 1 May 1998 |
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Keywords: | : Regulatory volume decrease — Ca2+ signaling — Acetylcholine — Secretion — Fura-2 |
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