Intravascular Concentrations of Calcium and Magnesium Ions and Edema Formation in Isolated Lungs

The perfusate concentration of Ca ++ has been assumed to be important for the permeability of the exchange vessels to proteins; low [Ca ++ ] is said to result in edema development. The possible role of perfusate [Mg ++ ] in this connection has previously not been considered. In the present work the correlation between the perfusate concentrations of Ca ++ and Mg ++ and edema development has been analyzed. In a perfused rabbit lung preparation edema developed at physiological intravascular pressures when the perfusate (plasma) [Ca ++ ] was reduced to about 7. 10 ‐5 mM and the [Mg ++ ] to about 1. 10 ‐3 mM by EDTA additions. Edema development was not seen at intravascular concentrations of Ca ++ and Mg ++ of about 4. 10 ‐5 and 4. 10 ‐1 mM, respectively. Such concentrations were achieved by addition of EGTA to the perfusate. Thus either the [Mg ++ ] or the [Ca ++ ] plus [Me ++ ] in the perfusate must be the important parameter for the edema development. The changes in the capillary permeability induced by EDTA‐additions were largely reversible by addition of Ca ++ . This effect of Ca ++ had a latency period of less than one min.