Abstract
A new enzymic method for blood levels of pyruvate kinase (PK) activity has been developed for the emergency clinical use. After preincubation of 20μl serum (or plasma) with 1 ml solution of enzyme and substrate at pH 7.4 for 3 min, PK activity was measured as increase of absorbance at 340 nm from 5 min to 10 min. Time-dependent increase of PK activity was observed from 6 min to 30 min, and a linear dilution curve was obtained by diluted human muscle PK and patient serum. intra- and inter-assay variations wereC.V.=3.0% and 2.4%, respectively. Analytical recovery of enzymic PK method was 93-107%. A significant correlation was noted between enzymic and colorimetric assay.
In 95 normal subjects, normal value of PK activity was 102±2.2 (mean±SEM) mIU/ml. Apparent increase of serum PK levels were observed in acute transmural myocardial infarction, with the mean peak value was 289±22.1 mIU/ml, which was 3 fold over than normal. Although serum levels of CK were elevated in subjects with hypothyroidism and post operation of chest-open surgery, serum levels of PK were not elevated.
These results indicate that the present assay kit for serum level of PK is clinically useful for the emergency diagnosis and follow up of myocardial infarction when measured simultaneously with CK.
