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, cytoplasma tic fractions and in the complete homogenate of the mouse hepatocytes follo wing injection of microcystin-YR and nodularin. The effect of both toxins d epended on the time of action and on the fraction of cell cytoplasm. Microc ystin-YR inhibited the synthesis of the studied proteases and caused a labi alization of lysosomal membranes, whereas nodularin induced the synthesis o f the enzymes and destabilised the reticulum endoplasmatic membranes. (C) 2 000 Elsevier Science Ltd. All rights reserved.