Isolation of parenchymal cell-derived particles from non-parenchymal rat liver cell preparations

Rat liver was perfused with collagenase and the non-parenchymal cells were isolated by means of differential centrifugation. Low magnification microscopical examination indicated that in this non-parenchymal cell fraction less than 1 % are parenchymal cells, whereas the observed pyruvate kinase kinetics indicated that 50% of the total amount of pyruvate kinase in this fraction is of parenchymal cell origin. The non-parenchymal cell fraction was further purified by metrizamide density cushion centrifugation followed by centrifugal elutriation. A fraction that consisted of small particles, diameter < 5 μm, was collected. The pyruvate kinase activity in this fraction showed characteristics of absolute L-type kinetics and further examination of these particles, called blebs, indicated that they were of parenchymal cell origin. Determination of enzyme markers with regard to the different subcellular structures indicated that the blebs, as compared with parenchymal cells, contained lower specific activities of enzyme markers for the endoplasmic reticulum, mitochondria and especially peroxisomes. Electron micrographs indicated the complete absence of nuclei. It is suggested that the pure isolated blebs form a unique test material to study the involvement of the nucleus and/or peroxisomes in metabolic processes. The identification of these blebs in the non-parenchymal cell preparations might also explain some discrepancies in the literature about the presence of certain metabolic processes in non-parenchymal cells.