Isolation, characterization, and attachment of rabbit distal colon epithelial cells

The authors investigated various enzymatic digestion procedures for isolating epithelial cells from the distal colon of New Zealand White male rabbits. Rabbit mucosa was washed, diced, and digested for 90 minutes in one of five different solutions, including a new combination consisting of 0.03% collagenase IV and 0.1% pronase (solution V). Solution I (0.3% dispase) yielded 14.2 +/- 8.2 x 10(6) colonocytes/g mucosa, solution II (0.15% dispase and 0.03% collagenase) yielded 7.7 +/- 2.8 x 10(6) colonocytes/g mucosa, and solution III (0.03% collagenase IV) yielded 15.4 +/- 10(6) cells/g mucosa. Solutions I-III have previously been described for the isolation of colonocytes. Solution IV (0.1% pronase and 325 U/mL DNAase) was originally described for the isolation of nasal epithelial cells but yielded only 2.5 +/- 1.2 x 10(6) cells/g mucosa when applied to the isolation of colonocytes. The new combination of pronase and collagenase, solution V, yielded significantly more colonocytes, 34.5 +/- 3.0 x 10(6) cells/g mucosa, than previously described methods (P less than 0.01). Inclusion of 5 mmol/L ethylenediaminetetraacetic acid in any of the solutions enhanced neither viability nor yield. The digestion product of solution V could be enriched for crypts by serial low-speed centrifugations. The epithelial origin of the colonocytes was confirmed by immunofluorescent staining for cytokeratins. Functional viability was tested by determining the presence of a Na+/H+ exchanger, using the pH fluorescent dye bis(carboxymethyl)-5(6)-carboxyfluorescein acetoxymethyl ester to measure intracellular pH. The authors document that sodium-dependent restoration of intracellular pH in colonocytes acid-loaded to a pH of 6.30 occurred at a rate of 0.19 +/- 0.02 pH U/min. Amiloride at concentrations of 1 mmol/L completely inhibited operation of the exchanger, as did sodium substitution with choline or tetramethylammonium. Lineweaver-Burke analysis at this intracellular pH showed a Michaelis constant of 10.71 mmol/L Na+ and a maximum velocity of 0.12 pH U/min. Exposing the colonocytes to 100 nmol/L phorbol 12,13-dibutyrate increased antiporter activity by 62.0%. Finally, the authors describe the synthesis of a new biomatrix composed of the basement membrane of 3T3 NIH fibroblasts that permits significantly improved colonocyte attachment than to glass, plastic, collagen types I or IV, or matrigel.