LYSOSOMAL ENZYME-ACTIVITIES IN PARENCHYMAL AND NON-PARENCHYMAL LIVER-CELLS ISOLATED FROM YOUNG, ADULT AND OLD RATS

Parenchymal and nonparenchymal cells were isolated from the livers of female rats, aged 3, 12, 24 and 30-35 mo., by means of enzymatic techniques. About 70% of the cells in the nonparenchymal cell suspensions were endothelial cells and 25% were Kupffer cells. More than 90% of the isolated parenchymal, Kupffer and endothelial cells were viable as judged by trypan blue exclusion and ultrastructural appearance. The age-related changes in the specific activities of the lysosomal enzymes acid phosphatase, .beta.-galactosidase, cathepsin D and arylsulfatase B in parenchymal and nonparenchymal cells showed no correlated behavior. The most prominent change was observed for the cathepsin D activity in parenchymal cells, which nearly triples during the lifespan of the rat. A comparison of the activities obtained with homogenates of the whole liver and with parenchymal and nonparenchymal cells revealed that aging changes in lysosomal enzyme activities in homogenates should be carefully interpreted, since opposite patterns of change were often observed for the activities in parenchymal cells and in nonparenchymal cells.