Hyperosmotic but not hyposmotic stress evokes a rise in cytosolic Ca2+ concentration in endothelium of intact rat aorta.
The effects of osmotic stress on the cytosolic Ca2+ concentration ([Ca2+]i) in the endothelium of excised intact rat aorta were investigated using the indicator fura-2 and the patch clamp technique. Hyperosmotic stress evoked a reversible rise in endothelial [Ca2+]i in the presence but not absence of extracellular Ca2+, indicating that it evoked Ca2+ entry without release from intracellular stores. Hyposmotic stress was without significant effect. Cytochalasins B and D reduced the effect of hyperosmotic stress but not acetylcholine on endothelial [Ca2+]i. In endothelium isolated from underlying smooth muscle, hyperosmotic stress produced a rise in the [Ca2+]i and depolarisation of the endothelial membrane potential whereas hyposmotic stress was without effect. Mechanosensitive cationic channels recorded in cell-attached patches were activated by hyperosmotic solutions applied to the endothelium and inhibited by hyposmotic solutions. These data suggest that shrinkage of endothelial cells evokes an increase in [Ca2+]i by opening a pathway for Ca2+ entry from the extracellular space. The mechanosensitive ionic channels which we have previously described may be responsible for this response.
Marchenko
S M
SM
Department of Physiology, University of Cambridge, Downing Street, Cambridge CB2 3EG, UK.
Sage
S O
SO
D000818:Animals; D001011:Aorta / Q000378:metabolism* / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D002412:Cations / Q000378:metabolism; D003599:Cytoskeleton / Q000502:physiology; D003600:Cytosol / Q000378:metabolism*; D004553:Electric Conductivity; D004730:Endothelium, Vascular / Q000378:metabolism* / Q000502:physiology; D066298:In Vitro Techniques; D007473:Ion Channels / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology; D009994:Osmolar Concentration; D009997:Osmotic Pressure; D051381:Rats; D013314:Stress, Mechanical
D002412:Cations; D007473:Ion Channels; D002118:Calcium