These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Role of cation gradients in hypercontracture of myocytes during simulated ischemia and reperfusion.
    Author: Nishida M, Borzak S, Kraemer B, Navas JP, Kelly RA, Smith TW, Marsh JD.
    Journal: Am J Physiol; 1993 Jun; 264(6 Pt 2):H1896-906. PubMed ID: 8322920.
    Abstract:
    We examined the relationship between transsarcolemmal cation gradients and hypercontracture of cardiac myocytes in ischemia and reperfusion using adult rat ventricular myocytes superfused with buffer mimicking normal or ischemic extracellular fluid. Contractile performance of electrically stimulated cells was recorded by an optical video system simultaneously with measurements of intracellular Ca2+ concentration ([Ca2+]i) using fura-2 or intracellular pH (pHi) using 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. While cells were exposed to simulated ischemia buffer, the transsarcolemmal H+ gradient was abolished, [Ca2+]i transient stopped, and twitch contraction of myocytes ceased. Upon reperfusion with normal buffer, H+ gradient was quickly restored, Ca2+ transients restarted with transient increase in systolic Ca2+, and twitch contraction restarted with development of hypercontracture, which continued after [Ca2+]i returned to preischemic level even in the presence of near-normal concentrations of high-energy phosphates. When the transsarcolemmal proton, Na+, and Ca2+ gradients were altered so that Na+ entry via Na(+)-H+ exchange and Ca2+ entry via Ca(2+)-Na+ exchange were made less favorable, the transient systolic overshoot of Ca2+ at reperfusion and development of hypercontracture was largely avoided. These results suggest that Na+ and then Ca2+ entry via the Na(+)-H+ and Na(+)-Ca2+ exchangers, respectively, probably contribute to the increase in [Ca2+]i and hypercontracture of myocytes at time of reperfusion in this model.
    [Abstract] [Full Text] [Related] [New Search]