1. The distribution of three membrane-bound enzymes, alkaline phosphatase, 5′-nucleotidase and γ-glutamyl transferase, has been examined in rat liver fractionated into parenchymal cells, a Kupffer cell fraction and a biliary tract fraction by perfusion with collagenase solution.

2. In control rat livers the highest enzyme concentrations were found in Kupffer cell preparations. The fraction enriched with biliary tract cells showed concentrations two- to fourfold those in isolated parenchymal cells.

3. At 24 h after ligation of the bile duct there was a fourfold increase in the alkaline phosphatase activity in parenchymal cells and a 2·5-fold increase of the same enzyme in the biliary tract fraction. The concentration of alkaline phosphatase in Kupffer cells remained unchanged.

4. 5′-Nucleotidase and γ-glutamyl transferase concentrations tended to decrease after bile-duct ligation for 24 h, the most marked changes being found in Kupffer cells.

5. After bile-duct ligation for 7 days the overall activities of hepatic alkaline phosphatase and γ-glutamyl transferase increased fourfold and there was a small rise in 5′-nucleotidase. For alkaline phosphatase and γ-glutamyl transferase the changes were found primarily in parenchymal cells and in the biliary tract fraction. There was a small rise in the activity of 5′-nucleotidase in parenchymal cells and a fall in activity in Kupffer cells.

6. These data show marked differences in the distribution and behaviour of three enzymes which are often used as alternatives in the assessment of patients with liver disease.

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