In earlier papers, we reported that the activity of
prolidase (EC 3.4.13.9) increased in the plasma of patients with
cirrhosis, while that of serum
prolinase (EC 3.4.13.8) was normal and was affected only by
necrosis. In this work, we investigated
prolinase and
prolidase activity during short and long-term CCL4 administration in the rat. After a single dose,
prolinase activity increased in serum faster than did
prolidase activity and it also decreased more slowly. Within the liver, no significant change in these two
enzyme activities was observed during the acute phase of
necrosis. During chronic CCl4 intoxication, the rises in
prolidase and
prolinase activity in rat serum were difficult to interpret, because of the liver
necrosis present throughout the experiment. However, within the liver,
prolinase activity was not affected, unlike that of
prolidase which rose at week 3, reached a maximum value at week 6 (reversible
fibrosis) and remained elevated at weeks 10 and 12 (irreversible
fibrosis). The increase in
prolidase activity was specific for liver and was not observed in other tissues. These results are in agreement with those obtained in humans; they highlight the possible physiological significance of enhanced liver
prolidase activity during the fibrotic process.