THE EFFECTS OF IRRADIATION AT DIFFERENT TIMES OF THE DAY ON RAT INTESTINAL GOBLET CELLS

Quantitative changes in jejunal goblet cells were studied in control a nd whole body irradiated rats using PAS-Alcian blue staining of crypt sections, A circadian dependence was observed when control animals wer e killed at different times during the light/dark cycle. Irradiation w ith 3 Gy produced a 2-3-fold increase within 36 h in goblet cells rela tive to controls, followed by a reduction to very low levels, There wa s a return to pre-treatment levels later than was observed for the col umnar cells. The present results on the pattern of response of goblet cells and those of brush border enzyme activity are consistent with th e hypothesis that ionizing radiation can influence differentiation. In fact during the first hours after irradiation an early induction of d ifferentiation is evident while during the early repopulation phase co lumnar cells prevailed relative to the goblet cells. Only at later tim es were normal differentiation patterns seen. Groups of animals expose d to the same dose of radiation at different times of the day showed s imilar general patterns of behaviour even if the group irradiated at m idnight showed a more marked and longer lasting injury.