Abstract
Like other cells of epithelial origin, MDCK cells respond with a reversible structural transformation to a diminution in the concentration of extracellular Ca2+. Upon deprivation of Ca2+ in the medium the cells undergo an active contraction mediated by the actin-myosin cytoskeleton, in parallel to detachment of the intercellular contacts and appearance of free spaces in the epithelium or monolayer (Castillo et al., 1998). We now present results indicating that the decrease of external Ca2+ plays an indirect and non-specific role in activating contraction, probably by allowing an influx of Na+. The omission of external Ca2+ had no effect when it was replaced by Mg2+, Ba2+ or Hg2+, and the addition of any of these divalent cations induced relaxation of cells previously contracted by exposure to low Ca2+. A null or weak response was observed also when Ca2+ was lowered in a solution where Na+ was replaced by choline or in the presence of amiloride (30 μM), which reduces the permeability of the plasma membrane to Na+. Restitution of Na+ or removal of amiloride were followed by contraction in the same cultures. Li+ proved an able substitute of Na+ as requisite for cell contraction in response to Ca2+ depletion. Monensin (0.1 mM) –an ionophore selective for Na+– and to a lesser extent ouabain (0.1 mM) –an inhibitor of Na+ extrusion across the plasma membrane– , both stimulated contraction in the presence of the normal level of external Ca2+. Decreasing by half the normal concentration of external K+ facilitated cell contraction, but typical responses were observed when K+ was increased to 40 mM by partial substitution for Na+. These findings attest that cell contraction in response to low Ca2+ is likely due to an increase in the permeability of the plasma membrane to Na+, though not to membrane depolarization as such. Evidences from other motile systems suggest that Na+ influx might in turn cause an elevation of cytoplasmic Ca2+, which activates the actin-myosin cytoskeleton.
Similar content being viewed by others
References
Allard B and Rougier O (1992) Reappraisal of the role of sodium ions in excitation-contraction coupling in frog twitch muscle. J Muscle Res Cell Motil 13: 117-125.
Anderson JM, Balda MS and Fanning AS (1993) The structure and regulation of tight junctions. Curr Opin Cell Biol 5: 772-778.
Baker PF and Umbach JA (1987) Calcium buffering in axons and axoplasm of Loligo. J Physiol (Lond.) 383: 369-394.
Britch M and Allen TD (1980) The modulation of cellular contractility and adhesion by trypsin and EGTA. Exp Cell Res 125: 221-231.
Burridge K and Chrzanowska-Wodnicka M (1996) Focal adhesions, contractility, and signaling. Annu Rev Cell Dev Biol 12: 463-519.
Caillé J, Ildefonse M, Rougier O and Roy G (1978) Evidence for an action of sodium ions in the activation of contraction of twitch muscle fibre. Pflgers Arch 379: 117-119.
Castillo AM, Lagunes R, Urbán M, Frixione E and Meza I (1998) Myosin II-actin interaction in MDCK cells: role in cell shape changes in response to Ca2. variations. J Muscle Res Cell Motil 19: 557-574.
Cereijido M, Meza I and Martínez-Palomo A (1981) Occluding junctions in cultured epithelial monolayers. Am J Physiol 240 (Cell Physiol 9): C96-C102.
Cuthbert AW, Fanelli GM and Scriabine A (1979) Amiloride and Epithelial Sodium Transport. Urban and Schwarzenberg, Balti-more-Munich.
Forman DS and Shain WG (1981) Batrachotoxin blocks saltatory organelle movement in electrically excitable neuroblastoma cells. Brain Res 211: 242-247.
Frixione E and Ruiz L (1988) Calcium uptake by smooth endoplasmic reticulum of peeled retinal photoreceptors of the crayfish. J Comp Physiol A 162: 91-100.
Fujimoto T and Ogawa K (1982) Energy-dependent transformation of mouse gall bladder epithelial cells in a Ca2.-depleted medium. J Ultrastruct Res 79: 327-340.
Garty H and Palmer LG (1997) Epithelial sodium channels: function, structure, and regulation. Physiol Rev 77: 359-396.
González-Mariscal L, Contreras RG, Valdés J, García-Villegas MR and Cereijido M (1994) Extracellular and intracellular regulation of junction assembly in epithelial cells. In: Citi S (ed.) Molecular Mechanisms of Epithelial Cell Junctions: From Development to Disease. (pp. 107-121) R G Landes Co., Austin.
Gow IF and Ellis D (1994) Transmembrane movement of lithium ions in isolated sheep heart Purkinje fibres. J Mol Cell Cardiol 28: 299-310.
Hitchcock S (1977) Regulation of motility in non muscle cells. J Cell Biol 74: 1-15.
Madara J and Pappenheimer JR (1987) Structural basis for physio-logical regulation of paracellular pathways in intestinal epithelia. J Membr Biol 100: 149-164.
Martínez-Palomo A, Meza I, Beaty G and Cereijido M (1980) Experimental modulation of occluding junctions in a cultured transporting epithelium. J Cell Biol 87: 736-745.
Matalon S, Benos DJ and Jackson RM (1996) Biophysical and molecular properties of amiloride-inhibitable Na. channels in alveolar epithelial cells. Am J Physiol 271 (Lung Cell Mol Physiol 15): L1-L22.
Meza I, Ibarra G, Sabanero M, Martínez-Palomo A and Cereijido M (1980) Occluding junctions and cytoskeletal components in a cultured transporting epithelium. J Cell Biol 87: 746-754.
Meza I, Sabanero M, Stefani E and Cereijido M (1982) Occluding junctions in MDCK cells: modulation of transepithelial perme-ability by the cytoskeleton. J Cell Biochem 18: 407-421.
Mondragón R and Frixione E (1989) Retinomotor movements in the frog retinal pigment epithelium: dependence of pigment migration on Na<Superscript>+</Superscript> and Ca<Superscript>2+</Superscript>. Exp Eye Res 48: 589-603.
Mondragón R and Frixione E (1992) Conditional inhibition of screen-ing-pigment aggregation by lidocaine in crayfish photoreceptors and frog retinal pigment epithelium. J Exp Biol 166: 197-214.
Ochs S (1982) Axoplasmic Transport and its Relation to Other Nerve Functions. (pp. 301-303) John Wiley & Sons, New York.
Palmer LG (1985) Interactions of amiloride and other blocking cations with the apical Na channel in the toad urinary bladder. J Membr Biol 87: 191-199.
Pappenheimer JR (1987) Physiological regulation of transepithelial impedance in the intestinal mucosa of rats and hamsters. J Membr Biol 100: 137-148.
Paulmichl M, Friedrich F and Lang F (1986) Electrical properties of Madin-Darby canine kidney cells. Effects of extracellular sodium and calcium. Pflügers Arch 407: 258-263.
Paulmichl, M, Gstraunthaler G and Lang F (1985) Electrical prop-erties of Madin-Darby canine kidney cells. Effects of extracellular potassium and bicarbonate. Pflügers Arch 405: 102-107.
Peña-Rasgado C, McGruder KD, Summers JC and Rasgado-Flores H (1994a) Effect of isosmotic removal of extracellular Ca2. and of membrane potential on cell volume in muscle cells. Am J Physiol 267 (Cell Physiol 36): C768-C775.
Peña-Rasgado C, Summers JC, McGruder KD, DeSantiago J and Rasgado-Flores H (1994b) Effect of isosmotic removal of extra-cellular Na. on cell volume and membrane potential in muscle cells. Am J Physiol 267 (Cell Physiol 36): C759-C767.
Pitelka DR and Taggart BN (1983) Mechanical tension induces lateral movement of intramembrane components of the tight junction. Studies on mouse mammary cells in culture. J Cell Biol 96: 606-612.
Pitelka DR, Taggart BN and Hamamoto ST (1983) Effects of extracellular calcium depletion on membrane topography and occluding junctions of mammary epithelial cells in culture. J Cell Biol 96: 613-624.
Potreau D and Raymond G (1982) Existence of a sodium-induced calcium release mechanismon frog skeletal muscle fibres. J Physiol (Lond.) 333: 463-480.
Prabhananda BS and Kombrabail MH (1998) Relative magnitudes of the rate constants associated with monensin-mediated H+, Na+ and K+ translocations across phospholipid vesicular membranes. Biochim Biophys Acta 1370: 41-50.
Pressman BC (1976) Biological applications of ionophores. Annu Rev Biochem 45: 501-530.
Vites AM and Wasserstrom JA (1996) Fast sodium influx provides an initial step to trigger contractions in cat ventricle. Am J Physiol 271 (Heart Circ Physiol 40): H674-H686.
Taub M and Saier Jr MH (1979) An established but differentiated kidney epithelial cell line (MDCK). Meth Enzymol 58: 49-50.
Weibel ER and Bolender RP (1973) Stereological techniques for electron microscopic morphometry. In: Hayat MA (ed.) Principles and Techniques of Electron Microscopy. Biological applications, Vol. 3. (pp. 237-296) Van Nostrand Reinhold Co., New York.
Worth RM and Ochs S (1982) Dependence of batrachotoxin block of axoplasmic transport on sodium. J Neurobiol 13: 537-549.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Lagunes, R., Ruiz, L. & Frixione, E. Contraction of epithelial (MDCK) cells in response to low extracellular calcium is dependent on extracellular sodium. J Muscle Res Cell Motil 20, 761–770 (1999). https://doi.org/10.1023/A:1005580425932
Issue Date:
DOI: https://doi.org/10.1023/A:1005580425932