Rate of Penetration of Ions through the Capillary Wall

Abstract

Summary. Solutions of labelled chloride, bromide, sodium, potassium, phosphate and deuterium oxyde were injected into the circulation of rabbits and the speed of the escape of the labelled ions from the plasma was determined. Potassium was found to penetrate at a much faster rate through the capillary wall than any other ion investigated. Information on the permeability of the muscle and brain capillaries were obtained by comparing the labelled sodium, phosphate and heavy water content of muscle and plasma, respectively brain and plasma. The muscle endothelium was found to be more permeable to sodium and to phospate than the endothelium of the brain. The partition ratio of labelled sodium between plasma and the chloride space of the brain amounts after the lapse of 11 min. only to 1/10 of the equilibrium value; during that time a proportional partition of labelled sodium between plasma and the chloride space of the muscle was obtained. In the course of an hour, somewhat less than 1/3 of the proportional partition of bromine between plasma and the grey brain substance was reached. Proportional partition of labelled water between plasma and the muscle water was reached after about half an hour. We wish to express our hearty thanks to Professor N iels B ohr for kindly putting numerous facilities at our disposal.