Abstract
Lactate dehydrogenase (LDH) activity in human plasma provides useful information for diagnoses of liver and heart diseases. However, LDH in human plasma inactivates during frozen storage. Therefore it is important to use fresh plasma for diagnosis. Sodium glutamate and glycerol are known to exert a cryoprotective effect on purified LDH. These cryoprotectants and sucrose also prevent the inactivation of LDH during extraction and purification processes. This paper deals with the effects of sodium glutamate to prevent the inactivation of LDH in human plasma during frozen storage. Sodium glutamate, glycerol and sucrose were almost equally successful in preventing the inactivation of purified LDH during frozen storage. Sodium glutamate prevented the inactivation of LDH in human plasma during frozen storage at -40°C and during cyclic freeze-thawing. Thus, for diagnosis of liver or heart diseases, it will be possible to store human plasma in a freezer after the addition of sodium glutamate.
