RESUMO
PURPOSE: The aim of this investigation was to determine whether pre- or post-administration of vitamin A will be effective in reducing the radiation-induced alterations in intestinal disaccharidases in rats. MATERIAL AND METHODS: Rats were subjected to fractionated whole-body irradiation (20 x 0.5 Gy). Intestinal lactase activity as well as maltase and sucrase activities were assessed. Vitamin A was administered at daily intraperitoneal dose of 15,000 IU/kg body weight for 7 days prior to radiotherapy and thereafter twice weekly throughout therapy up to 7 days post irradiation. RESULTS: In irradiated rats a marked decrease in intestinal lactase activity to about one-fourth of those in non-irradiated rats was observed. In addition, a significant reduction in maltase and sucrase activities to one half of the control group was observed. The application of vitamin A significantly improved the radiation-induced inhibition of intestinal enzymes. Pretreatment application of vitamin A is more efficient to protect against radiation injury than a posttreatment application. CONCLUSIONS: The usage of vitamin A for modulation of radiation-induced changes in intestinal enzymes provides sufficient protection against treatment side effects induced by large volume radiotherapy.
