Subcellular Fractionation of Rectal Biopsy Homogenates from Patients with Inflammatory Bowel Disease

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Abstract
Rectal biopsy specimens from control subjects and from patients with Crohn's colitis. non-rectal Crohn's disease, and acute ulcerative colitis were homogenized in isotonic sucrose and subjected to analytical subcellular fractionation by sucrose density gradient centrifugation. The gradient fractions and tissue homogenates were assayed for marker enzymes for the principal organelles: 5′nucleotidase (plasma membrane). malate dehydrogenase (mitochondria), catalase (peroxisomes), lactate dehydrogenase (cytosol), N-acetyl-bT-glucosaminidase (lysosomes). and neutral-a-glu-cosidase (endoplasmic reticulum). In normal tissue there was a distinct plasma membrane peak at density 1.12 g/ml. In tissue from patients with Crohn's disease the activity was increased approximately twofold even when the rectum showed no evidence of histological involvement. A second plasma membrane component was noted in Crohn's disease at density 1.19 g/ml. The total activity of the mitochondrial enzyme was similar in the various patient groups, but there was evidence of mitochondrial damage. There were no significant alterations in activity and density gradient distributions of catalase or of neutral aL-glucosidase in the various patient groups, although less membrane-bound lactate dehydrogenase was noted in the patients with inflammatory bowel disease. There was a reduction of both cytosolic and particulate N-acetyl-bT-glucosaminidase in ulcerative colitis and a selective reduction in particulate activity in non-rectal Crohn's disease, demonstrating lysosomal alterations in these disorders. These results indicate selective and specific alterations in the principal subcellular organelles, especially the plasma membrane, lysosomes, and mitochondria, in the inflammatory bowel disease.