[${^3H}Ryanodine$ Binding Sites of SR Vesicles of the Chicken Pectoral Muscle

To investigate the properties of ryanodine binding sites of the bird skeletal SR vesicles, SDS PAGE, purification of RyR, and $[^3H]ryanodine$ binding study were carried out in the SR vesicles prepared from the chicken pectoral muscle. The chicken SR vesicles have two high molecular weight (HMW) protein bands as in eel SR vesicles on SDS PAGE. The HMW bands on SDS PAGE were found in the $[^3H]ryanodine$ peak fraction $(Fr_{3-5})$ obtained from the purification step of the ryanodine receptor protein. Bmax and KD of the chicken $[^3H]ryanodine$ binding sites were 12.52 pmol/mg protein and 14.53 nM, respectively. Specific $[^3H]ryanodine$ binding was almost maximal at $50{\sim}100$ ${\mu}M$ $Ca^{2+}$, but was not increased by 5 mM AMP and not inhibited by high $Ca^{2+}$. Binding was significantly inhibited by $20{\sim}100$ ${\mu}M$ ruthenium red and 1 mM tetracaine, but slightly inhibited by $Mg^{2+}$. From the above results, it is suggested that chicken SR vesicles have the ryanodine binding sites to which the binding of ryanodine is almost maximal at $50{\sim}10$ ${\mu}M$ $Ca^{2+}$, is significantly inhibited by ruthenium red and tetracaine, slightly inhibited by $Mg^{2+}$, but not affected by AMP and not inhibited by high $Ca^{2+}$.