Enhancement of brush border membrane peptidase activity in rat jejunum induced by starvation

Conflicting results have been obtained in previous studies concerning the a daptation of intestinal brush border membrane enzymes to starvation. This s tudy was designed to clarify the changes in these enzymes under starvation conditions, using a molecular biological approach. Sprague-Dawley rats were starved or given total parenteral nutrition (TPN) for 5 days. Rats allowed free access to food were used as controls. Changes in the activity and exp ression of jejunal brush border membrane enzymes were compared between thre e groups. In the starved group, aminopeptidase N and dipeptidyl peptidase I V activity was significantly elevated to 177% and 166%, respectively, of co ntrol values. In contrast, sucrase and maltase activity was significantly d ecreased. The activity of these peptidases also tended to be increased at t he renal brush border membrane. Up-regulation of peptidase activity was not evident in the TPN group. Western and Northern blot analysis revealed that the changes in aminopeptidase N activity were attributable to increases in the protein and mRNA level. The activity and expression of brush border me mbrane peptidases in rat jejunum is up-regulated during starvation, and the se changes are considered to be an effect of whole-body malnourishment, rat her than an absence of luminal nutrition.