A comparative study of lysosomal enzyme activity in monocytes and Kupffer cells isolated simultaneously in a rat model of liver injury.

Macrophages have been isolated and cultured in vitro from normal rat livers and from livers into which macrophages have been recruited in vivo, following an intravenous injection of killed Corynebacterium parvum. Simultaneously, peripheral blood monocytes have been isolated and cultured in vitro. After 24 hr in culture, supernatants and cell lysates were harvested and the activity of a lysosomal enzyme, N-acetyl-glucosaminidase (NAG), measured. NAG activity in the cell lysates of the recruited tissue macrophages was significantly higher than that measured in control tissue macrophages. Increased NAG activity was also observed in the supernatants from the recruited macrophages. In contrast, the NAG activity in cell lysates and supernatants of peripheral monocytes was not significantly changed after C. parvum injection. In this animal model, measurement of a lysosomal enzyme produced by peripheral monocytes did not reflect the magnitude of the changes observed for the tissue macrophages.