Water uptake and energy metabolism in brain slices from the rat.

1. Exchange of (3)H(2)O with H(2)O takes place rapidly in incubated rat brain slices but at a lower rate in slices from infant brain than from adult brain. The temperature coefficient (Q(10)) of the exchange process, between 37 and 4 degrees C, is 1.76 with infant brain and 1.26 with adult brain. The exchange process is unaffected by the presence of ouabain or 2,4-dinitrophenol. 2. An approximately linear relationship exists between water uptake and the concentration of ATP in the incubated slices in the presence of various concentrations of glucose. Little or no change occurs in water uptake and ATP concentration in the presence of a glucose concentration exceeding 3mm. A linear relationship also exists between the water uptake and ATP concentration in the presence of 10mm-glucose and various concentrations of sodium l-glutamate but the line is parallel to that found with changed glucose concentrations and shifted in the direction of increased water uptake. A similar parallel relationship exists between water uptake and ATP concentration in the presence of 2,4-dinitrophenol, but the amount of water uptake is significantly smaller in the presence of 2,4-dinitrophenol than in its absence. 3. Copper chloride (0.3mm) or mercuric chloride (0.3mm) both increase water uptake and diminish the ATP concentration in slices. Sodium malonate (2mm) or sodium d-glutamate (10mm) has similar effects. 4. Substances, or conditions, affecting water uptake in incubated brain slices may be divided roughly into two classes in accordance with their effects on adenosine triphosphatase and membrane permeability, but there may be considerable lack of specificity.