Stability of commonly used thiols and of human creatine kinase isoenzymes during storage at various temperature in various media.

We assessed the stability--at 20, 4 --20, and --80 degrees C--of 2-mercaptoethanol, dithioerythritol, and dithiothreitol, and of semi-purified creatine kinase isoenzymes of human origin in the presence and absence of the three compounds. The isoenzymes plus the sulfhydryl compounds were also assessed an aqueous buffer, in heat-inactivated pooled sera, or in fresh pooled sera with low endogenous total creatine kinase. We also examined the influence of thawing conditions from--20 or--80 degrees C, of fast freezing, and of exposure to fluorescent light. At 20 and 4 degrees C some--SH groups are oxidized. At--20 and--80 degrees C this loss is diminished. It is a function of both temperature and diluent. For stability, creative kinase isoenzymes stored at any temperature require the presence of a suitable sulfhydryl compound. Periodic addition of fresh sulfhydryl solutions stabilized creatine kinase isoenzymes suspended in the two protein-based diluents by 10-30%; for those in an aqueous buffer such additions decreased the activity to stored creatine kinase isoenzymes. Fast freezing does not increase recovery of creatine kinase isoenzyme activity over slow freezing at--80 or--20 degrees C. Thawing should be done as infrequently as possible and should be done rapidly, at 37 degrees C, for the residual enzyme activity to be maximal.