ANESTHETICS ALTER THE PHYSICAL AND FUNCTIONAL-PROPERTIES OF THE CA-ATPASE IN CARDIAC SARCOPLASMIC-RETICULUM

We have studied the effects of the local anesthetic lidocaine, and the general anesthetic halothane, on the function and oligomeric state of the Ca-ATPase in cardiac sarcoplasmic reticulum (SR). Oligomeric chan ges were detected by time-resolved phosphorescence anisotropy (TPA). L idocaine inhibited and aggregated the Ca-ATPase in cardiac SR. Micromo lar calcium or 0.5 M lithium chloride protected against lidocaine-indu ced inhibition, indicating that electrostatic interactions are essenti al to lidocaine inhibition of the Ca-ATPase. The phospholamban (PLB) a ntibody 2D12, which mimics PLB phosphorylation, had no effect on lidoc aine inhibition of the Ca-ATPase in cardiac SR. Inhibition and aggrega tion of the Ca-ATPase in cardiac SR occurred at lower concentrations o f lidocaine than necessary to inhibit and aggregate the Ca-ATPase in s keletal SR, suggesting that the cardiac isoform of the enzyme has a hi gher affinity for lidocaine. Halothane inhibited and aggregated the Ca -ATPase in cardiac SR. Both inhibition and aggregation of the Ca-ATPas e by halothane were much greater in the presence of PLB antibody or wh en PLB was phosphorylated, indicating a protective effect of PLB on ha lothane-induced inhibition and aggregation. The effects of halothane o n cardiac SR are opposite from the effects of halothane observed in sk eletal SR, where halothane activates and dissociates the Ca-ATPase. Th ese results underscore the crucial role of protein-protein interaction s on Ca-ATPase regulation and anesthetic perturbation of cardiac SR.