[Light sensitivity of creatine kinase in control sera].

The light sensitivity of creatine kinase in different control sera was investigated. Control sera were dispensed into reaction vessels, then exposed for 4 h at 25 degrees C to a light source equivalent in intensity to normal laboratory illumination. In 12 out of 22 control sera, the catalytic concentration of the creatine kinase fell by 25-63%. Under the same conditions, in patient sera, creatine kinase is stable. In the "light sensitive" control sera, the instability of the enzyme increased with the intensity of illumination. When exposed to sunlight creatine kinase was unstable in all the investigated control and patient sera. The addition of mercaptoethanol stabilized the creatine kinase in "light sensitive" control sera. The reason for the different light sensitivity of different control sera is not known.