TY - JOUR
T1 - Effects of hypoxia, acidosis, and simulated ischemia on repriming of caffeine contracture in rat myocardium
AU - Shimizu, Motoyoshi
AU - Kimura, Shinichi
AU - Myerburg, Robert J.
AU - Bassett, Arthur L.
N1 - Funding Information:
*This work was supported by National Heart, Lung, and Blood Institute Grants-in-Aid from the American Heart Association, Greater Miami Chapter grant from the Florida Affiliate.
Copyright:
Copyright 2014 Elsevier B.V., All rights reserved.
PY - 1990/6
Y1 - 1990/6
N2 - This study was designed to examine the effects of hypoxia, acidosis, glucose-free medium and their combination on contraction and sarcoplasmic reticulum (SR) function in rat ventricular trabeculae. The isometric twitch tension was measured during superfusion with hypoxic (PO2 < 30 mmHg), acidic (pH 6.80), glucose-free, or their combined ("ischemic") Tyrode's solution at 20°C. The time needed to fully recover the contraction induced by 10 mm caffeine (repriming time) was measured to indirectly estimate the Ca2+ uptake of the SR. In "ischemia" and acidosis, the peak developed tension decreased progressively for the first 30 min (37.6 ± 9.2% and 56.6 ± 8.4% of control at 30 min, respectively), and then became steady. In hypoxic solution, the peak developed tension decreased moderately for the first 30 min (86.8 ± 4.8% of control at 30 min), and thereafter remained steady. Developed tension did not change significantly during 60 min of superfusion with glucose-free solution. The repriming time of caffeine contraction was significantly delayed in both "ischemic" and hypoxic solutions, but was unchanged in acidic and glucose-free solutions. These results lead us to suggest that depressed SR function to accumulate Ca2+ may contribute to the decline in tension in ischemia and hypoxia, but that other mechanisms are important in the tension decline induced by acidosis.
AB - This study was designed to examine the effects of hypoxia, acidosis, glucose-free medium and their combination on contraction and sarcoplasmic reticulum (SR) function in rat ventricular trabeculae. The isometric twitch tension was measured during superfusion with hypoxic (PO2 < 30 mmHg), acidic (pH 6.80), glucose-free, or their combined ("ischemic") Tyrode's solution at 20°C. The time needed to fully recover the contraction induced by 10 mm caffeine (repriming time) was measured to indirectly estimate the Ca2+ uptake of the SR. In "ischemia" and acidosis, the peak developed tension decreased progressively for the first 30 min (37.6 ± 9.2% and 56.6 ± 8.4% of control at 30 min, respectively), and then became steady. In hypoxic solution, the peak developed tension decreased moderately for the first 30 min (86.8 ± 4.8% of control at 30 min), and thereafter remained steady. Developed tension did not change significantly during 60 min of superfusion with glucose-free solution. The repriming time of caffeine contraction was significantly delayed in both "ischemic" and hypoxic solutions, but was unchanged in acidic and glucose-free solutions. These results lead us to suggest that depressed SR function to accumulate Ca2+ may contribute to the decline in tension in ischemia and hypoxia, but that other mechanisms are important in the tension decline induced by acidosis.
KW - Acidosis
KW - Caifeine
KW - Contractile function
KW - Hypoxia
KW - Sarcoplasmic reticulum
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U2 - 10.1016/0022-2828(90)91012-V
DO - 10.1016/0022-2828(90)91012-V
M3 - Article
C2 - 2231737
AN - SCOPUS:0025124866
VL - 22
SP - 697
EP - 705
JO - Journal of Molecular and Cellular Cardiology
JF - Journal of Molecular and Cellular Cardiology
SN - 0022-2828
IS - 6
ER -