Pulmonary Transcapillary Exchange of ²⁴Na and ⁵¹CrEDTA. An Evaluation of Factors Influencing the Extraction of these Tracers during one Passage through an Isolated Lung Preparation

Abstract

NICOLAYSEN, G . Pulmonary transcapillary exchange of P4Na and S I C r E D T A . A n evaluation of factors influencing the extraction of these tracers during onepassage through an isolated lung preparation. Acta physiol. scand. 1971. 82. 3 9 3 4 0 5 , Experiments with the single injection indicator diffusion method have been carried out in an isolated, ventilated and plasma-perfused rabbit lung preparation. A mixture of two diffusible tracers (24Na, W r E D T A ) and one intravascular reference tracer ( 12jI-albumin) were used. Relative concentrations in the first indicator-containing venous outflow fractions collected indicated that there had been some initial extraction of the diffusible indicators. A small extravascular space of distribution appeared to represent the most important determinator for the extent of this initial extraction during one single passage through the vascular bed. Results from several types of experiments were consistent with there being also some moderate degree of diffusion limitation for the extraction of the diffusible tracers. Extraction of the diffusible tracers appeared to be moderately increased when the intravascular concentrations of both Ca++ and Mg++ were reduced to such low levels that edema was developing in the preparation. I t appears unlikely though that the single injection indicator diffusion method in its present form can yield more detailed information on capillary permeability to small solutes in this rabbit lung preparation.

Pulmonary O2 transfer during pulsatile and non‐pulsatile perfusion

“…In order to avoid vasomotion and uncontrolled variations in vascular resistance 15 mg papaverine chloride was added to the perfusate. By alternating between the two perfusion circuits, maintaining constant mean flow, the effect of switching from low to high F,oz could be studied repeatedly during the Hauge & Nicolaysen (1971) found that the lung preparation used in the present studies had normal ultrastructure without interstitial edema after several hour\ of perfusion with pulsatile plasma flow at physiological vascular pressures and normal vascular resistance.…”

“…the transit of Evans blue through the lungs during pulsatile and non-pulsatile flow was examined. The experimental setup was identical to that described above, except that the total venous outflow from the preparation could be diverted to a rapid sampling system (Nicolaysen 1971). By this system the outflow from the lungs could be sampled in split fractions with one sample per 0.67 s. Since the total outflow could be sampled there was no recirculation.…”

Permeability and Pore Radii of Pulmonary Capillaries in Rabbits of Different Ages

“…However, the velocity of flow in pulmonary capillaries is likely to be similar to that for systemic capillaries, since although fewer in number the pulmonary capillaries have a wider diameter than systemic capillaries (Folkow & Neil, 1971). Nicolaysen (1971) found decreasing extraction of both Na' and EDTA with time in the isolated plasma-perfused rabbit lung. Both molecules showed a parallel rate of decrease.…”

“…Crone (1 963), using a similar technique, found negligible extraction of sucrose and inulin by the lungs and concluded that the indicator diffusion method was unsuitable for tissues with high perfusion rates. Nicolaysen (1971) found significant extraction of both %Na and "Cr-EDTA, which decreased rapidly with time in the isolated rabbit lung. Since he found only small differences in permeability between normal lungs and those made oedematous with EDTA, the author concluded the technique was insensitive.…”