Transcapillary efflux of gamma globulin in rabbit skeletal muscle

Abstract

Previous studies of macromolecular transport from blood to lymph have measured the net flux of protein across the capillary wall. Present studies were designed to establish the presence of, and measure the rate of, interstitial to luminal transport of iodinated gamma globulin in the isolated perfused gastrocnemius muscle of the rabbit.

Iodinated gamma globulin was injected intravenously and allowed to circulate in rabbits for 18–19 hr. The gastrocnemius muscle was vascularly isolated and perfused with tracer-free artificial plasma. A vascular marker, ⁵⁹Fe-transferrin, was used to measure washout of the muscle vasculature.

Efflux of gamma globulin from the interstitium to capillary lumen occurred and at the rate of 0.004–0.023 min⁻¹. The iodinated protein leaving the muscle after vascular washout was examined and 82–91% was found to have properties identical to that of gamma globulin. Capillary permeability measured before perfusion and again during perfusion with artificial plasma showed no change.

The present measure of efflux rate is higher than some other estimates although this is not surprising since it is a measure of largely a unidirectional flux. Estimates of vesicular transit time in capillary endothelial cells, based on the presently determined efflux values, ranged from 0.1 to 0.5 sec.