Inhibition of isoproterenol positive atrial chronotropic effect by methylmethacrylate polymer and monomer

Atria from rats exposed in vivo to methylmethacrylate polymer or monomer were superfused and chronotropic responses to isoproterenol determined. Control and polymer-exposed atria superfused with oxygen-saturated buffer yielded dose-response curves which were essentially identical with regard to maximal increase and potency of isoproterenol. Control atria superfused with buffer containing 70% of possible oxygen saturation showed a 10-fold decrease in isoproterenol potency and a maximal effect approximately 75-80% that of fully oxygenated atria. Atria exposed to methylmethacrylate polymer and superfused with 70% oxygen saturated buffer showed a 100-fold decrease in isoproterenol potency and a maximal effect approximately 25% that of fully oxygenated control atria. Exposure of rats to methylmethacrylate monomer in vivo resulted in complete abolition of the chronotropic response to isoproterenol in atria superfused with 70% oxygen saturated media.