Effects of pH on the stability of the indium-113m blood protein complex and the selective binding of indium-113m to transferrin

Noninvasive evaluation of acute capillary permeability changes during high-volume ventilation in rats with and without hypercapnic acidosis

OBJECTIVE

To evaluate whether hypercapnic acidosis attenuates acute alterations of pulmonary capillary permeability due to high lung stretch in rats using a simple, noninvasive, scintigraphic method.

DESIGN

Prospective, randomized, controlled animal study.

SETTING

University research laboratory.

SUBJECTS

Male adult Wistar rats weighing 291 +/- 7.5 g.

INTERVENTIONS

Three groups of rats were studied: controls ventilated with a low (6 mL/kg body weight) tidal volume and rats ventilated with a high (38 mL/kg body weight) tidal volume under normocapnic (Paco(2) = 35.2 +/- 1.65 mm Hg) or hypercapnic (Paco(2) = 102.5 +/- 5.63 mm Hg) conditions.

MEASUREMENTS AND MAIN RESULTS

Pulmonary capillary permeability alterations were assessed by monitoring the rate of (111)In-transferrin accumulation in lung tissue. Respiratory system pressure-volume curves were registered and analyzed. High tidal volume ventilation increased In-transferrin plasma to lung flux in such a way that I(111)In-transferrin behaved like a marker of water. The rate of initial (first 30 mins of high tidal volume ventilation) lung transferrin accumulation measured by scintigraphy (standardized lung/heart ratio) was steady, correlated with the percent decrease in respiratory system compliance (a marker of edema progression), and did not differ between normocapnic and hypercapnic groups (18.9 +/- 3.97 vs. 14.2 +/- 2.89%/hr, not significant). However, lung In-tranferrin accumulation rate was highly scattered due to variable interindividual mechanical properties of the respiratory system. This rate was correlated with initial values of volume of the upper inflection point of the pressure-volume curve (r = -.53, p < .001) and end-inspiratory pressure (r = .54, p < .001). Mechanical properties were similar in normocapnic and hypercapnic rats. There was no difference between In-transferrin accumulation rates in these rats when a stringent selection was made based on end-inspiratory pressure (28-32 cm H(2)O) or body weight (330-360 g).

CONCLUSIONS

Hypercapnic acidosis does not influence in vivo the acute increase in pulmonary capillary permeability due to high-volume ventilation.

Metabolism of receptor targeted 111In-DTPA-glycoproteins: identification of 111In-DTPA-epsilon-lysine as the primary metabolic and excretory product

The hepatic and renal retention of indium-111 (111In) from 111In-labeled polypeptides has been the subject of many investigations. Because the lysosome is a common intracellular destination for the degradation of polypeptides, we studied the lysosomal metabolism of 111In-DTPA-labeled glycoproteins targeted to cell surface receptors in vitro and in vivo. We found that 111In-DTPA-glycoproteins were degraded to 111In-DTPA-epsilon-lysine, which was slowly released from cells and recovered intact in urine and feces. These results suggest a mechanism for 111In retention at target and non-target sites.

Lung protein leakage in feline septic shock

The aim of the present study was to explore lung microvascular leakage of protein and water in a feline model of septic shock, using a double isotope technique with external gamma camera detection and gravimetric lung water measurements. The experiments were performed on artificially ventilated cats. One group of cats (n = 8) was given an infusion of live Escherichia coli bacteria, and another group (n = 5) served as a control group receiving saline. Plasma transferrin was radiolabeled in vivo with indium-113m-chloride, and erythrocytes were labeled with technetium-99m. The distribution of these isotopes in the lungs was continuously measured with a gamma camera. A normalized slope index (NSI) was calculated, indicative of the transferrin accumulation corrected for changes in local blood volume that reflect protein leakage. In the septic group there was a protein leakage after bacterial infusion, with a NSI of 39 x 10(-4) +/- 5 x 10(-4) min-1 (mean +/- SEM), and the PaO2 diminished from 21 +/- 1 to 9.5 +/- 1 kPa. In control cats a slight protein leakage with a NSI of 9 +/- 10(-4) +/- 2 x 10(-4) min-1 was detected, probably caused by the operative procedure, but PaO2 did not change. Wet-to-dry-weight ratios of postmortem lungs were not significantly different between the groups. It was concluded that an intravenous infusion of live E. coli bacteria induces a lung capillary protein leakage without increased lung water and a concomitantly disturbed gas exchange.(ABSTRACT TRUNCATED AT 250 WORDS)

External 113Inm and 99Tcm radiation detection of lung edema induced by oleic acid in the guinea pig

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.