Effects of Ischemic Preconditioning on Ventricular Function and Ryanodine Receptors of Cardiac Sarcoplasmic Reticulum in Dogs
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Previous studies have shown that myocardial ischemia causes a reduction in the number of of cardiac ryanodine receptors. However, how ischemic preconditioning(IP) affects the density of ryanodine receptors remains uncertain. To clarify the effect of IP on ryanodine receptors, the density of high-affinity 3H-ryanodine binding sites and thedissociation constant for ryanodine of the myocardium were examined in anesthetized open chest dogs with or without IP. Group S(n=6); 5 minute-inchemia was followed by 10 minute-reperfusion as IP. Group C(n=5); 20 minute-inchemia was performed without IP. GroupP(n=6); 20 minute-inchemia was perfomed following IP. Myocardium from risk and non-risk areas were obtained for the subsequent purification of sarcoplasmic reticulum misrosomal fraction. Hemodynamic parameters showed no significant differences between group C and group P after 20-minute ischemia. However, density of ryanodine receptors in ischemic region was significantly reduced in group C compared to that in non-ischemic region (7.3±0.7 versus 11.3±1.4 pmol/mg protein; p < 0.05). When preconditioned, the reduction of density of ryanodine receptors in ischemic region was significantly attenuated (11.6±1.4 versus 12.7±0.9 pmol/mg protein). Just after IP procedure, density of ryanodine receptors in the ischemic region did not change significantly compared to the non-ischemic region (10.3±0.5 versus 9.8±0.5 pmol/mg protein). Thus, IP attenuated the down regulation of ryanodine receptors after sustained ischemia, which should play an important role in the recovery of myocardial function after reperfusion.
- Yamaguchi University Graduate School of Medicineの論文
Yamaguchi University Graduate School of Medicine | 論文
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