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The expression of enzymes in LLC-PK1 and MDCK cells was used to study the retention of differentiated properties of the renal epithelial cell lines by a biochemical approach. Activities of marker enzymes, for which intracellular and intranephron localization is known, were determined from crude cell homogenates of LLC-PK1 and MDCK monolayer cultures. The activity patterns of the particular enzymes found were then compared with the in vivo distribution of the enzymes along the rat nephron. LLC-PK1 cells exhibit high activities of apical membrane enzymes when compared with MDCK cells, whereas in the latter high activity of Na-K-ATPase could be detected. The activities of lysosomal enzymes, mitochondrial enzymes, and transaminases were higher in LLC-PK1 than in MDCK cells. Glycolytic enzymes, however, displayed identical activity levels in both the LLC-PK1 and MDCK cells, which may be due to the fact that these are continuous cell lines and to the culture conditions used, since glucose is a major energy source in the culture media.
Gstraunthaler et al. (Mon,) studied this question.