Modification of the Fractionated γ-Radiation-Induced Alteration in the Na + /K + -ATPase Activity of Radiosensitive Tissues by Vitamin A

The effect of pre or post-administration of vitamin A in ameliorating the radiation-induced alteration in intestinal and spleen Na+/K+-ATPase activity of rats was determined. Rats subjected to multifractionated γ-radiation (20 × 0.5 Gy) over the whole-body showed a significant reduction in Na+/K+-ATPase activity being more obvious in spleen than in intestine. Administration of vitamin A at a daily i. p. dose of 15,000 IU/kg bd. wt. for 7 days prior to fractionated γ-irradiation and thereafter twice weekly throughout the exposure period (as pretreatment regimen) or following the end of irradiation for 7 days (as posttreament regimen) afforded a significant protection from radiation-induced inhibition of spleen and intestinal Na+/K+-ATPase activity. Even though, pretreatment regimen is more efficient against radiation injury to this enzyme than posttreatment, so that its activity was nearly normalized in the first regimen. The regeneration of normal enzyme activity in the tissues of the vitamin A-pretreated group suggests that the intestinal and spleen epithelia in presence of vitamin A are rendered relatively radioresistant.