Bile acid biosynthesis during liver regeneration: enzyme activities of cholesterol 7alpha-hydroxylase and 3beta-hydroxy-delta5-C27-steroid dehydrogenase in rats.

The effects of two-thirds partial hepatectomy on bile acid metabolism have not been well established. This study investigated the changes in microsomal enzymes activities during liver regeneration. The cholesterol 7alpha-hydroxylase (7alpha-hydroxylase) and 3beta-hydroxy-delta5-C27-steroid dehydrogenase (3beta-dehydrogenase) activities in male Wistar rats were determined using high-performance liquid chromatography (HPLC). Cytochrome P450 (P450) and cytochrome b5 (b5) levels and NADPH cytochrome c reductase activities were also determined after hepatectomy. 7alpha-Hydroxylase activities were not reduced on days 3, 5, or 7 compared to those of sham-operated rats, but there was a significant decrease (by 60%) of 3beta-dehydrogenase activity compared to that of sham-operated groups (p <0.01) on days 3, 5, and 7 after hepatectomy. While 7alpha-hydroxylase activity had recovered by day 3 after hepatectomy, 3beta-dehydrogenase activity had not, even on day 7. These results suggest that the mechanisms of regulation of these 2 bile acid metabolizing enzymes are significantly different during liver regeneration.