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Enhancement of Halothane Action at the Ryanodine Receptor by Unsaturated Fatty Acids

Elsevier Inc.
DOI: 10.1016/s1054-3589(08)60625-0
  • Biology


Publisher Summary This chapter summarizes various studies to extend published findings in skeletal muscle regarding the actions of fatty acids. In the absence of anesthetics, the fatty acids can cause Ca2+ release in skeletal muscle and rabbit cardiac muscle by mechanisms independent of the Ca2+ release channel. Similar interactions could occur with other proteins, such as the Na+ channel, that also has its function altered by halothane and fatty acids. However, significant interactions of free fatty acids with the Ca2+ release channel and Na+ channel are somewhat unlikely under normal circumstances in an intact cell, as the fatty acids are bound to fatty acid-binding proteins in the cytoplasm. Although fatty acids probably have very little impact on Ca2+ regulation in the absence of anesthetics, their augmentation of net halothane-induced Ca2+ release is dramatic. Whereas the concentration of fatty acid required for this effect exceeds that of the normally unbound form, halothane could likely displace fatty acids from fatty acid-binding proteins. Considering the low concentration of fatty acids present and the resistance of the cardiac preparation to fatty acid-albumin complexes, it is unlikely that displacement of fatty acids by halothane plays a significant role in anesthetic action in rat cardiac muscle. Human or porcine skeletal muscle contains about 5 to 10 times as much free fatty acid as cardiac muscle. The huge potency of fatty acid-albumin complexes in their interaction with halothane in skeletal muscle compared to rat cardiac muscle suggests some actual association of fatty acid-binding proteins with the ryanodine receptor.

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