Endogenous quinidine-like immunoreactivity in the serum of rats with cardiac overload, stress or hyperthyroidism. Rapid communication.

: Quinidine-like immunoreactivity (Abbott TDx Quinidine fluorescence polarization immunoassay) was measured in control, sham-operated, abdominal aorta stenotic and hyperthyroid (thyroxine feeding 0.1 mg/rat/day rats. The mean quinidine levels (mumol quinidine/1 serum) were 0.07, 0.14, 0.13 and 0.25, respectively. The elevation in experimental hyperthyroidism was statistically (analysis of variance, Duncan's test) significant. The possibility of the existence of an endogenous antiarrhythmic, immunologically cross-reacting in quinidine immunoassay, is discussed.