Carbonic anhydrase I reduction in colonic mucosa of patients with active ulcerative colitis.

Ulcerative colitis (UC) is associated with low intracolonic pH and unbalanced transmucosal ionic exchanges. Along the gastrointestinal tract carbonic anhydrase isoenzyme I (CA-I) is specifically expressed in colon epithelium and is involved in mucosal control of ion, fluid, and acid-base balance. Since altered CA-I expression may play some role in UC, CA-I was measured at the mRNA and protein level and carbonic anhydrase (CA) enzyme activity was determined in colon biopsies of 14 UC patients (6 remission, 4 mild, 4 moderate UC) and of 12 healthy subjects. Patients with mild or moderate UC showed a significant reduction of CA-I mRNA and protein and of total CA activity in the inflamed mucosa compared to controls. Patients with UC in remission showed a pattern of CA-I expression and CA activity similar to controls. This is the first report showing a reduction in the expression of CA-I in active UC.