Sources of Variation in a Standardized and a Semi-micro Procedure for the Spectrophotometric Assay of Serum Glutamic-Oxalacetic Transaminase Concentration

1. Both a standard method and a semi-micro method for the spectrophotometric assay of serum glutamic-oxalacetic transaminase (S-GOT) concentrations have been described. 2. Either procedure is associated with an error defined by a factor of less than 1.03. 3. The temperature dependence of the rate of transamination was shown to follow Arrhenius' law over the range of temperature from 25° to 38°. 4. A tabulation of temperature factors calculated from the derived Arrhenius equation was presented. These factors permit correction of rates observed at temperature T to rates expected at 32°. 5. A comparison of normal S-GOT values from various sources was made, with correction for temperature differences. Based on 779 values from four different laboratories, the combined mean for adults was 21.9. 6. A standard unit of transaminase activity was defined and referred to as a Karmen unit. A Karmen unit represents that amount of transaminase in 1 ml. of sample which will cause a decrease in optical density at 340 mµ of 0.001 per minute at a temperature of 32°, an effective light path of 1 cm., and a volume of test solution of 3 ml. According to this definition, the mean normal adult S-GOT concentration is 21.9 Karmen units. The practical upper limit of normal will be defined in another publication.