External¹¹³In^m and⁹⁹Tc^m radiation detection of lung edema induced by oleic acid in the guinea pig

Summary

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 of¹¹³In^m labeled transferrin, a macromolecular marker, and⁹⁹Tc^m 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 accumulated¹¹³In^m-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 × 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.