WATER DISTRIBUTION IN INCUBATED SLICES OF BRAIN AND OTHER TISSUES

Abstract

Slices of rat cerebral cortex swell about 40% during one hour's aerobic incubation in bicarbonate-buffered medium. Thiocyanate or sucrose added to the medium equilibrate with part of the tissue fluid leaving a "non-thiocyanate" or "non-sucrose" space equal to about 45% of the total fluid which was present in the fresh unincubated slice. This space does not change with the extent of swelling or the time during which the tracer is present. The swelling thus appears to be extracellular. Inuilin in the medium equilibrates with little more than the water of swelling and docs not appear to enter the rest of the extracellular fluid. The swelling thus seems to involve uptake of fluid which is not continuous with the true tissue fluids. With glutamate or high potassium in the medium, swelling is increased and the non-thiocyanate, non-sucrose, and non-inulin spaces increase correspondingly. This increase is apparently intracellular. Swelling is also increased under anaerobic conditions. Results with sucrose and inulin indicate that this increase is due to intracellular swelling. The space occupied by thiocyanate increases with the time during which the thiocyanate is present in the medium under anaerobic conditions. Swelling can be decreased but not prevented by colloids in the medium. Medium rendered hypertonic with sucrose apparently causes cell shrinkage, as judged by the non-thiocyanate or non-sucrose space, without preventing uptake of "swelling water". Liver and kidney slices swell about 10%. Thiocyanate occupies the whole of the tissue fluid while inulin leaves a constant non-inulin space, equal to about 60% of the total fluid of the fresh unincubated slice. Sectors of diaphragm swell about 15%. Thiocyanate and inulin occupy about equal spaces. The non-thiocyanate and non-inulin spaces are about 49% of the total fluid of the fresh tissues. Diaphragm cut into strips parallel to the circumference swells more and thiocyanate and inulin penetrate most of the fluid. Sciatic nerve swells nearly as much as brain. The swelling is reduced if the ends are tied. Thiocyanate penetrates the tissue progressively with time. Inulin seems to occupy little more than the water of swelling, as in brain.