Unconventional dose administrations: modifications of body and small intestine weights.

: The modifications of body and small intestine weight were analyzed after abdominal irradiation in rats. Different doses were administered in single sessions, in two equal fractions with different splits, in multiple daily fractionations, varying the amount of the dose and the intervals among fractions. The results show that body weight gradually decreased after irradiation and only after many days it returned to control levels. Small intestine weight decreased starting from early intervals, and a rapid increase over controls was observed at 5 days. A return to control levels was reached later. Multiple-daily-fractionation (MDF) irradiation with 12 Gy (1200 rad) produced modifications less evident that the same dose administered in single session and appeared more similar to those observed after 6 or 8 Gy, according to the different splits used. The more marked the damage the lower the interval between fractions when a total dose of 12 Gy was administered in two fractions. The modifications after 6 Gy MDF were less marked than after a single session of the same magnitude, both in body and small-intestinal weight. In conclusion the MDF used in these experiments produced a damage very easily recovered by the organism in spite of the short time of dose administration.