Interstitial exclusion of albumin in rabbit lung measured with the continuous infusion method in combination with the wick technique.
OBJECTIVE
To determine albumin exclusion from the pulmonary perivascular interstitium by using the continuous infusion methods coupled with direct samples of pulmonary interstitial fluid via the wick technique.


METHODS
To evaluate extracellular albumin distribution volume, radioactive ((125)I) rabbit serum albumin (RSA) was delivered intravenously until reaching a steady-state tissue concentration. In anesthetized rabbits with ligated kidney pedicles, extracellular (V(x)) and intravascular (V(v)) fluid volumes were measured as the distribution volumes of (51)Cr-ethylenediaminetetraacetic a id and (131)I-RSA, respectively. Post mortem, lung samples and interstitial fluid collected via implanted wicks were assayed for isotope activity. The extravascular wick fluid equivalent albumin distribution volume (V(a,w)) was calculated assuming equal concentrations of (125)I-RSA in interstitial and wick fluid.


RESULTS
The mean (+/-SE) V(x), V(v), and interstitial fluid volumes (V(i) = V(x) - V(v)) were 1896 +/- 61 (n = 8), 556.8 +/- 19, and 1329 +/- 73 microL/g of blood-free dry lung tissue weight, respectively. The mean albumin-excluded volume (V(e,a) = V(i) - V(a,w) and the excluded fraction (V(e,a)/V(i)) were 875.8 microL/g +/- 58 and 0.66 +/- 0.05, respectively.


CONCLUSIONS
At variance with previous indirect reports, the present data indicate that normal pulmonary parenchyma displays a tight fibrous structure that is highly restrictive with respect to plasma protein distribution.
Negrini
Daniela
D
Department of Biomedical, Experimental Clinical Sciences, University of Insubria, Varese, 21100, Italy. Daniela.Negrini@uninsubria.it
Tenstad
Olav
O
Wiig
Helge
H
D000818:Animals; D045604:Extracellular Fluid / Q000737:chemistry*; D005110:Extracellular Space / Q000378:metabolism; D007263:Infusions, Parenteral; D007457:Iodine Radioisotopes; D008168:Lung / Q000033:anatomy & histology* / Q000098:blood supply / Q000378:metabolism; D011817:Rabbits; D012709:Serum Albumin / Q000032:analysis* / Q000378:metabolism; D014018:Tissue Distribution
D007457:Iodine Radioisotopes; D012709:Serum Albumin