Noninvasive measurement of pulmonary transvascular protein flux in sheep

Publisher Website
Google Scholar
Abstract
A new, noninvasive method was used to measure the net transvascular flux of 113mIn-transferrin (MW 76,000) in lungs of intact sheep. By means of an external scintillation detection probe the apparent increase in lung plasma volume with time was determined after giving an i.v. bolus of the tracer protein. Pulmonary blood volume was measured using 99mTc-labeled red blood cells (RBC). The measured increase in plasma volume is due to the diffusive and convective transfer of the labeled protein from the vascular space. This indirect estimate of protein flux was compared to that measured independently as the rate of tracer protein accumulation in lung lymph. Protein flux was measured under base-line conditions (n = 10), after Pseudomonas aeruginosa bacteremia (n = 6) and during elevation of left atrial pressure (n = 3). At time zero, 5 mCi of 99mTc-RBC and 10 mCi of 113mIn-transferrin were injected. The .gamma.-emissions of the 2 isotopes over the lung were counted using a 3-in NaI crystal, focused to a field 4 cm in diameter and 14 cm inside the chest. In all 19 studies, interstitial accumulation of tracer protein by external radioflux detection correlated well with the directly measured accumulation in lung lymph. The pulmonary vascular transfer coefficient markedly increased after bacteremia. External radioflux detection appears to be a valid measure of transvascular protein flux in lung. This method may be used to study changes in protein transfer when direct sampling of lung lymph is not desirable or feasible.

This publication has 5 references indexed in Scilit: