Influence of microcystin-YR and nodularin on the activity of some proteolytic enzymes in mouse liver

The activity of cathepsins D and L, arginine aminopeptidase, dipeptidase II and dipeptidase IV was determined in the lysosomal, microsomal, cytoplasmatic fractions and in the complete homogenate of the mouse hepatocytes following injection of microcystin-YR and nodularin. The effect of both toxins depended on the time of action and on the fraction of cell cytoplasm. Microcystin-YR inhibited the synthesis of the studied proteases and caused a labialization of lysosomal membranes, whereas nodularin induced the synthesis of the enzymes and destabilised the reticulum endoplasmatic membranes.