CAPILLARY PERMEABILITY: RATE OF TRANSCAPILLARY EXCHANGE OF IRON ADDED TO PLASMA AS RADIOACTIVE FERRIC BETA1-GLOBULINATE

Abstract

With ferric beta1-globulinate tagged with radioactive iron as the tracer material, the rate of transcapillary exchange of iron has been determined in the guinea pig. From 0.3 to 1% of the iron of the plasma is exchanged per minute. Previous expts. with deuterium oxide have shown that 146% of the water of the plasma is exchanged per minute with extravas-cular water. On the assumption that iron crosses the capillary wall as ferric beta1-globulinate, it can be said consequently that the capillaries are at least 100 times more permeable to water than to the globulinate. It appears that tagged ferric globulinate prepd. by intravascular injn. of radioferric chloride into a donor animal followed by exsanguination 30 min. later, is acceptable for measurement of plasma volume in laboratory animals.