The establishment of a small animal model for studies of lung injury is in great demand. Therefore, a double radioisotope labeling method was applied to study the dynamics of lung injury with protein-rich edema in the anesthetized guinea pig. One external scintillation detector was placed over the lung and another over the heart, where they continuously sampled the energy spectrum of 113Inm labeled transferrin, a macromolecular marker, and 99Tcm labeled red blood cells (RBC), a blood pool marker. Lung injury was induced by i.v. oleic acid in doses of 0.03 and 0.06 ml/kg b.wt. infused for 10 min. We calculated the rate of increase of accumulated 113Inm-transferrin in the lung corrected for blood pool changes. Macromolecular leakage showed a graded response in regression line-slope (RLS) to oleic acid. Both oleic acid groups showed significantly different RLSs as compared to the saline control (mean +/- SD x 10(-3) min-1; 0.03 ml: 3.86 +/- 1.01 (n = 7); 0.06 ml: 10.75 +/- 4.06 (n = 6), and control 1.12 +/- 1.19 (n = 6]. Assays of changes of acid-base balance, cell dynamics, and lung wet-dry weight were in accordance with the occurrence of lung edema. The RLS was well correlated with the lung wet-dry weight (r = 0.98). We conclude that measurements of pulmonary edema in guinea pigs can be performed quantitatively with the aid of external detection of radiolabeled transferrin and RBC:s. Thus, the method could be useful in further studies on mechanisms and/or treatment of protein-rich lung edema.

Indium-113m (t1/2 = 100 min; gamma-emission of 393 keV) in trace amounts was injected i.v. in rats. Blood was collected by heart puncture 15 min after the injection, and blood plasma was separated by centrifugation. Gel filtration of plasma on Sephadex G-25M equilibrated with glycine/HCl (pH 2.2-3.6), NaHCO3/CO2 (pH 4.0-11.0) glycine/NaOH (pH 8.6-10.6) or sodium acetate/acetic acid (pH 3.0-5.0) was used to separate free indium from indium bound to macromolecular proteins. Determination of radioactivity in eluted fractions showed that more than 85% of the plasma indium was bound to macromolecules at pH values between 5.0 and pH 10.6. However, dissociation of the indium plasma protein complexes occurred at pH values below 5.5, and more than 90% of the indium radioactivity was found in the low molecular weight fraction at pH 2.2. Affinity chromatography using immobilized antibodies to rat transferrin was used to isolate transferrin at pH 7.4 and 5.5. Immunodiffusion and electrophoresis were used to identify the proteins in fractions obtained by affinity chromatography. It was found that the indium-113m activity was correlated with the content of transferrin and that 80%-90% of this activity was found in fractions that had affinity to antitransferrin. These fractions contained transferrin exclusively at pH 7.4, but additional protein fractions of albumin and alpha1-globulin mobility at pH 5.5. At pH 7.4 and 5.5, 10%-20% of the indium activity was detected in molecular fractions that had no affinity to antitransferrin. Immunologic analyses showed that these fractions contained transferrin.(ABSTRACT TRUNCATED AT 250 WORDS)

A guinea pig model was developed to document the association of polymorphonuclear neutrophils (PMN) decrease with pulmonary leakage after a sublethal infusion of endotoxin (LPS Escherichia coli 0111:B4, 5 µg/min/kg). A control group was prepared in the same manner and given an infusion of vehicle alone. Severe leukopenia developed, mostly expressed in the neutrophil population. There was a decrease in RBC catalase and fibronectin. Plasma leakage in the lung followed the endotoxin infusion, which could indicate endothelial cell damage. The results from the present study suggest an activation of PMN in endotoxin-infused animals, degranulation and release of toxic oxygen species, resulting in pulmonary plasma extravasation.

The distribution of systematically injected In-113m (t1/2 = 100 min) in organs of the rat was analyzed, and the use of the isotope for in vivo and in vitro gamma-radiation detection studies of blood plasma protein extravasation was demonstrated in skin, muscle, and tumor. In-113m was slowly excreted from rats. One to 6 h after injection the blood held 3% and 2%, respectively, of injected radioactivity/g tissue wet weight; skin and muscle held 0.1%-0.2%/g; liver, colon, and spleen held approximately 1%/g; lungs 1.5%-1.3%/g and kidneys 2.8%-3.3%/g. Scintillation camera technique revealed 40%-80% extraaccumulation of In-113m in a control extremity upon local administration of serotonin and 20%-40% in an extremity with a transplanted tumor, thus indicating a lower effect of serotonin in tumor microvascular circulation than in muscle and skin. In vitro detection of In-113m radiation by a well-counter in dissected tissues showed no effects of serotonin in the tumor and a four- to five-fold increase of radioactivity in muscle and skin, thus confirming blood protein extravasation upon serotonin treatment in these tissues. External analyses of In-113m in the vascular system using one miniaturized probe directed toward an area of interest showed that the method was too sensitive to movements of the animal, and second probe directed toward a control area is needed.