A method for the simultaneous and continuous monitoring of vascular tone and protein leakage in the synovium

Abstract

A technique has been developed to monitor changes in synovial vascular tone and leakage of macromolecules, two of the cardinal features of inflammation. The technique permits not only quantitative sequential measurements of the leakage of 125I-albumin from the circulation into the synovium, but also semiquantitative continuous monitoring of the leakage changes. It allows simultaneous continuous monitoring of changes in synovial vascular tone as well. Vascular protein leakage was monitored semiquantitatively by measuring the radioactivity of 125I-albumin in synovial perfusate when passed through a flow cell consisting of a plastic tubing coil situated inside the well of a gamma detector. Quantitative measurements were provided by collecting and counting the synovial perfusate for 125I-albumin. Synovial vascular tone was monitored continuously by measurement of the change in joint radiation emitted by in vivo-labelled 99m-Tc erythrocytes. The in vivo labelling procedure yielded an 86% ± 9% labelling efficiency. The degree of erythrocyte labelling was stable throughout the course of the experiment. Using this technique, the abilities of histamine to induce changes in synovial vascular tone and protein leakage were examined. Intraarticular infusion of 1 ng/mL histamine produced a 61% ± 24% increase in synovial vascular blood volume, but did not significantly increase 125I-albumin leakage above that produced by Krebs solution alone. Higher concentrations produced a concentration-related increase in the leakage of 125I-albumin, which was not accompanied by appreciable increases in synovial vascular blood volume above the basal line. The simultaneous and continuous monitoring provided by this technique has revealed an apparent dissociation between vascular tone and vascular protein leakage in response to intraarticular histamine.