LOSS OF SOLUBLE MATERIALS FROM IRRADIATED THYMOCYTES IN VITRO

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Abstract
Following exposure to X-radiation in doses above 100 r, rat thymocytes lose soluble compounds into the extracellular fluid during incubation in Krebs–Ringer solution at 37 °C and pH 7.4. Acid-soluble ribonucleotide and potassium ion concentrations in the irradiated cells decreased markedly after an initial lag period of 1 hour, during which the irradiated thymocytes could not be distinguished from control cells. These losses were accompanied by a gradual depolymerization of deoxyribonucleic acid. At least one labile enzyme, deoxycytidylate deaminase, also became inactivated. A similar loss of nucleotides and potassium ion from the thymus gland also occurred following its irradiation in the intact animal.A decrease in pH or temperature during incubation of irradiated thymocyte suspensions minimized the loss of potassium from the cells; the same treatments were found previously to decrease the sensitivity of these cells to the lethal effects of X-radiation. The loss of soluble materials appeared to be related to subsequent death of the cells. However, rapid loss of intracellular potassium from thymocytes is probably due to a breakdown of intracellular binding structures rather than to inhibition of active ion transport.