A study of the fluid uptake of rat kidney slices in vitro.

Rat renal cortical and medullary tissues show a marked elevation of relative water content when immersed in "physiological solutions" containing sodium and chloride ions, or in equally concentrated solutions of monosaccharides. In contrast to this, no increase in relative water content occurs in isosmotic solutions of three disaccharides studied. It appears to be unlikely that the fluid uptake is a result of intracellular hypertonicity existing either physiologically or pathologically. A more satisfactory alternative hypothesis is that ingress of water accompanies entrance of solutes (ions, monosaccharide molecules) into the tissue cells.