In an attempt to better understand the effect of whole body irradiation on the spontaneous motility and oxygen consumption rate of the isolated mouse duodenum, a whole body X-irradiation of 1,000r. was given to albino mouse, and 1) the total length of contraction of isolated duodenum was recorded on kymograph every five minutes for 60 minutes, 2) glucose and 5-hydroxytryptamine(5-HT) were added to the reaction medium of Kreb s-Ringer-bicarbonate buffer(KRB) and response of the isolated duodenum to the drugs was observed, and 3) the oxygen consumption rate (QO2) of the isolated duodenum as well as the effect of glucose and 5-HT on QO2 were measured by Warburg s standard manometric method and the comparison was made with the control(i.e. normal) group. The results thus obtained are summarized as follows. 1. The spontaneous motility of the isolated duodenum in the irradiated groups showed a significantly elevated pattern for the first 15 minutes comparing with the control. The motility, however, decreased after 15 minutes and remained so in the irradiated groups to the level of the nonirradiated control, but 24 hours post-irradiation group showed a tendency of an increased motility while one hour post-irradiation group showed no difference comparing with the control. 2. Addition of glucose produced generally elevated motility of the isolated duodenum in both irradiated and non-irradiated groups comparing with the control throughout the experiment, but no difference was observed in contractile amplitude between the irradiated and non¡¤irradiated groups. 3. When 5-HT was added to the irradiated group, the contractile amplitude of isolated duodenum was similar to that of the control, and 5-HT alone caused a slight increase of the motility comparing with the control. 4. The oxygen consumption rate (QO2) of the isolated duodenum was found to be ,slightly increased in one hour post¡¤irradiated group, but similar in 24 hour post¡¤irradiated group comparing with the control. Glucose produced a significant increase of QO2 in all the groups, but 5-HT produced a tendency of decrease of QO2 in all the groups.
