Transcapillary Loss,Equilibrium Time,Half-Return Time of Thiocyanate and Heavy Water in the Forearm. ∗

Abstract

Summary and Conclusions

A method is presented for determining under physiological conditions the net bidirectional exchange of permeable tracer substances across the capillary walls of the human forearm. 1. In the early period, maximum net transcapillary loss for thiocyanate was 49 ± 19% and for deuterium oxide 90 ± 4%. 2. The equilibrium time or period of net loss averaged 111 ± 66 seconds for SCN and 130 ± 86 seconds for D₂O. Equilibrium times for both SCN and D₂O were related directly to blood flow. 3. The half-return time for SCN averaged 3 ± 3.0 times the equilibrium time. In the cases in which simultaneous measurements were made the half-return time of D₂O averaged twice that of SCN.