Measurements of intestinal cell production at several sites throughout the gastrointestinal tract were compared using two different methods, namely tritiated thymidine to determine the uptake of tritium per unit weight of tissue (dpm/mg) and per microdissected intestinal crypt or stomach gland (dpm/crypt or gland) and the metaphase arrest technique, in the same group of rats. The metaphase arrest technique was employed to determine the crypt cell production rate per hour (CCPR). The dpm/crypt or gland of tritiated thymidene-derived tritium in microdissected intestinal crypts or stomach glands showed a good linear correlation (r=0.93) with CCPR which extrapolated through the origin. The dpm/mg wet weight of tissue showed a good linear correlation with CCPR (r=0.87) and dpm/crypt (r=0.97); however, neither of these relationships extrapolated through the origin. Instead there was a positive intercept of dpm/mg tissue which represented about 25-30% of the maximal tritium content of the intestine. This radioactivity in tissue had no counterpart in the crypts or glands and presumably reflected unbound tritium and tritium in cells which were located outside the epithelial compartment. The good linear correlation (r=0.93) between dpm/crypt and CCPR extended to the intestine of transected and 75% small bowel resected rats. Subsequent analysis of the times recorded for these procedures showed that determination of CCPR was faster by at least 25% than measurement of dpm/crypt. In conclusion, dpm/crypt but not dpm/mg tissue gave a valid estimate of intestinal cell production equivalent to measurement of CCPR. However, the metaphase arrest technique was faster, provided smaller relative errors, and gave a more direct measure of cell production and is therefore preferred.
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