Reduction of radiation damage to Tradescantia chromosomes by adenosine triphosphate, proline, and histidine.

N 1963, we reported that Tradescantia microspores treated with histidine or I proline prior to irradiation in helium showed fewer chromosome aberrations than the controls. In 1960 and 1962, similar results were obtained when material was pretreated in ATP, agreeing in general with the results that WOLFF and LUIPPOLD (1956) found in their work with Vicia faba. In 1960, we demonstrated by postirradiative treatments that the ATP effect was on the recovery process. In this report, similar experiments have demonstrated that histidine and proline also are operative during the recovery process. Numerous experiments have been performed (BEATTY and BEATTY 1960, 1962) to demonstrate the extent of the biological effects of ATP in irradiated cells. Preor posttreatment in an ATP solution for 1 % hours at 30°C in helium reduces the aberration yield by 50%. Treatment in ATP in helium reduces to 41% the aberration yield due to treatment in helium alone for 400 min. Aberration yield due to irradiation at 40°C in helium is reduced to 29% by treatment in an ATP solution. Recently we have carried out biochemical and radiobiological experiments involving ATP (BEATTY and BEATTY 1965). Using the luciferin-luciferinase assay for ATP under several experimental conditions, the ATP content in the protoplasm of Tradescantia microspores was found to be relatively constant. However, 1% hours treatment in an ATP solution will double the amount of ATP in the liquid surrounding the microspores, the periplasmodium. Conditions such as anoxia which deplete the ATP in the periplasmodium, increase the aberration yield. Since the amount of ATP within the microspores seems to be constant, the firefly technique cannot be used to demonstrate the passage of materials from the periplasmodium into the microspores. Radiobiological studies, using ATP32 alpha, beta, gamma-labeled, showed radioactivity in the protoplasm of the microspores in all materials treated with radioactive ATP solutions, but more than twice the activity in the material which was also irradiated. The present report deals with a more detailed study of the ATP, histidine, and proline effects on radiation recovery using both aberration yield and the luciferinluciferinase assay for ATP as experimental procedures.