Intracellular Ca2 Modulation during Short Exposure to Ischemia-Mimetic Factors in Isolated Rat Ventricular MyocytesReportar como inadecuado

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Collegium antropologicum, Vol.33 supplement 2 No.2 December 2009. -

We investigated the effects of different ischemia-mimetic factors on intracellular Ca2+ concentration Ca2+i. Ventricular myocytes were isolated from adult Wistar rats, and Ca2+i was measured using fluorescent indicator fluo-4 AM by confocal microscopy. Intracellular pH was measured using c5-and-6-carboxy SNARF-1 AM, a dual emission pH-sensitive ionophore. Myocytes were exposed to hypoxia, extracellular acidosis pHo 6.8, Na-lactate 10 mM, or to combination of those factors for 25 min. Monitoring of Ca2+i using fluo-4 AM fluorescent indicator revealed that Ca2+i accumulation increased immediately after exposing the cells to Na-lactate and extracellular acidosis, but not during cell exposure to moderate ischemia. Increase in Ca2+i during Na-lactate exposure decreased to control levels at the end of exposure period at extracellular pH 7.4, but not at pH 6.8. When combined, Na-lactate and acidosis had an additive effect on Ca2+i increase. After removal of solutions, Ca2+i continued to rise only when acidosis, hypoxia, and Na-lactate were applied together. Analysis of intracellular pH revealed that treatment of cells by Na-lactate and acidosis caused intracellular acidification, while short ischemia did not significantly change intracellular pH. Our experiments suggest that increase in Ca2+i during short hypoxia does not occur if pHi does not fall, while extracellular acidosis is required for sustained rise in Ca2+i induced by Na-lactate. Comparing to the effect of Na-lactate, extracellular acidosis induced slower Ca2+i elevation, accompanied with slower decrease in intracellular pH. These multiple effects of hypoxia, extracellular acidosis, and Na-lactate are likely to cause Ca2+i accumulation after the hypoxic stress.

intracellular Ca2+; intracellular acidosis; ischemia

Autor: Danijel Pravdić - ; Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, USA Nikolina Vladić - ; Department o



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