Cell kinetic study of murine jejunal crypts during multiple doses per day

We studied cell kinetics of mouse jejunal crypts during multiple fractionation using double labeling methods. Mice were irradiated to the total body once a day or twice a day. Fraction size was 2 Gy. Overall time was 1, 3 and 5 days. Labeling index (LI), duration of S phase (Ts) and potential doubling time (Tpot) were assessed next morning following the irradiation schedule. Mice were administered both bromo-deoxyuridine (BrdUrd) and 3H-Thymidine ([3H]dT) with a constant interval. Removed jejunum were stained with immuno-histochemistry and, then, processed for autoradiography. BrdUrd and [3H]dT LIs were the same and were increased up to 5 days despite the fractionation schedule. After 1 day following 2 fx/day, both Ts and Tpot decreased significantly. For 1 fx/day treatment, neither Tpot nor Ts changed. After 5 day following 1 and 2 fx/day, both Ts and Tpots were the same and Tpots were significantly shorter than that obtained from control. It seems that proliferative responses between 1 and 2 fx/day were different.