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AIM: To explore whether the differential effects of Zn2+ on ryanodine binding to the sarcoplasmic reticulum (SR) of skeletal and cardiac muscles resulted from different permeability of the SR to Zn2+. METHODS: [3H]ryanodine binding assays were performed to examine the effect of Zn2+ on ryanodine binding to the SR in the presence of pyrithione sodium (PyNa), a specific Zn2+ ionophore. RESULTS: As a control, PyNa up to 50 μmol/L did not induce any effect on ryanodine binding to the SR of cardiac muscle. But PyNa 1-100 μmol/L increased ryanodine binding in skeletal muscle with maximum binding (222.2 %±20.9 % of the control) and inhibited ryanodine binding to 50 % of the control at about 500 μmol/L. In the presence of PyNa 10 and 50 μmol/L the dose-dependence of the effect of Zn2+ in cardiac muscle was still monophasic and not changed by PyNa, while the biphasic effect of Zn2+ in skeletal muscle became monophasic. CONCLUSION: Different permeability of the SR to Zn2+ may account for the differential effects of Zn2+on ryanodine binding in skeletal and cardiac muscles. PyNa is not a strictly specific Zn2+ ionophore.
AIM: To explore whether the differential effects of Zn2 + on ryanodine binding to the sarcoplasmic reticulum (SR) of skeletal and cardiac muscle resulted from different permeability of the SR to Zn2 +. METHODS: [3H] ryanodine binding assays were performed to examine the effect of Zn2 + on ryanodine binding to the SR in the presence of pyrithione sodium (PyNa), a specific Zn2 + ionophore. RESULTS: As a control, PyNa up to 50 μmol / L did not induce any effect on ryanodine binding to the SR of cardiac muscle. But PyNa 1-100 μmol / L increased ryanodine binding in skeletal muscle with maximum binding (222.2% ± 20.9% of the control) and inhibited ryanodine binding to 50% of the control at about 500 μmol / L. and 50 μmol / L the dose-dependence of the effect of Zn2 + in cardiac muscle was still monophasic and not changed by PyNa, while the biphasic effect of Zn2 + in skeletal muscle became monophasic. CONCLUSION: Different permeability of the SR to Zn2 + may accoun t for the differential effects of Zn2 + on ryanodine binding in skeletal and cardiac muscles. PyNa is not a strictly specific Zn2 + ionophore.