An improved method for determination of colonic mucosal proliferation: uptake of tritiated thymidine under hyperbaric oxygen conditions.

In vitro uptake of tritiated thymidine under normal oxygen tension in standard tissue culture conditions (95% O2 and 5% CO2, 1 atm pressure) may only approximate the in vivo concentration of oxygen delivered to the colon epithelium in situ. Using standard O2 pressure conditions, however, generally good results are obtained. Incubation of tissues under slightly hyperbaric oxygen conditions has been reported to facilitate the uptake of thymidine in vitro and could permit greater sensitivity in calculating labeling indices. In this study we have compared measurements of colonic cellular proliferation by quantifying labeled cells in mouse colon by measuring DNA synthesis in rat colon exposed in vivo or in vitro to tritiated thymidine. In vitro incubations were performed in normal and hyperbaric oxygen conditions. We conclude that the hyperbaric oxygen technique markedly improves the uptake of thymidine in the colon and affords greater sensitivity in determining actual colonic labeling profiles.