The role of calcium in the volume regulation of rat lacrimal acinar cells.
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.
Speake
T
T
Cell Physiology Group, School of Biological Sciences (G.38), University of Manchester, Manchester, M13 9PT, UK.
Douglas
I J
IJ
Brown
P D
PD
D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D048429:Cell Size; D002478:Cells, Cultured; D065101:Chloride Channel Agonists; D018118:Chloride Channels / Q000378:metabolism; D016257:Fura-2; D007765:Lacrimal Apparatus / Q000166:cytology* / Q000378:metabolism; D018715:Microscopy, Video; D009997:Osmotic Pressure; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction; D013050:Spectrometry, Fluorescence
D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D065101:Chloride Channel Agonists; D018118:Chloride Channels; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D002118:Calcium; D016257:Fura-2