The effects of high concentrations of an electrolyte on the swelling of non-metabolizing tissue slices.

1. Rat kidney cortical slices, with metabolism suppressed by iodoacetate, were incubated anaerobically at 26 degrees C in hyperosmotic saline media. Changes in tissue composition with time, up to 12 hr, were studied. Despite initial shrinkage, gross swelling occurred, even in saline media of more than twice the concentration of normal extracellular fluid.2. The composition of non-metabolizing kidney slices incubated at 26 degrees C in a balanced saline medium containing 7 g polyethylene glycol 6000 (PEG 6000)/100 ml. was determined at intervals up to 12 hr. The tissue water, sodium and chloride contents had reached constant levels by 6 hr. Potassium continued to leak slowly from the tissue, but there was no significant further loss between 10 and 12 hr.3. Non-metabolizing kidney slices were incubated in PEG medium containing additional quantities of either a non-electrolyte (400 m-osmole glucose/kg H(2)O) or an electrolyte (400 m-osmole NaCl/kg H(2)O), both of which penetrated the tissue to attain approximately uniform concentrations in cells and media. Whereas the slices in the glucose medium attained the same equilibrium water content as those incubated in PEG medium alone, the final water content of slices in the medium containing additional NaCl was significantly lower. This difference might have resulted from depression of intracellular colloid osmotic pressure by the high salt concentration.