Inactivation of creatine kinase in physiological saline solutions

To determine the optimal conditions for measuring the activity of creatine kinase released from isolated skeletal muscle preparations, we investigated the stability of the enzyme during storage in saline solutions of varying composition. Parameters studied were temperature, presence of albumin or dithiothreitol, calcium concentration and anionic composition. It is concluded that maximal activity is retained when samples are kept at 4 degrees C and analyzed within 24 hours in the presence of a thiol-protective compound. If longer storage periods are anticipated, inactivation is significantly retarded by addition of albumin or by decreasing the free calcium concentration of the storage salines.