The effects of alloxan and histamine on the permeability of the pulmonary alveolocapillary barrier to albumin.

1. [(131)I]albumin transport from alveolus to perfusion fluid was evaluated in an isolated dog lung lobe preparation perfused at constant pressure with homologous plasma. The alveoli were filled with a 1:1 mixture of Ringer-Tyrode solution and plasma.2. For twenty-three lung lobes, an average control permeability coefficient of the alveolocapillary membrane for albumin was found to be 1.9 x 10(-9) cm/sec with a range of (0.3-5.5) x 10(-9) cm/sec.3. Alloxan in concentrations of 0.22-2.50 mg/ml. perfusate was observed to increase the alveolocapillary membrane permeability to [(131)I]albumin with a positive correlation between dose and effect. The larger doses of alloxan increased the permeability by a factor of ten or more.4. Glutathione (GSH), administered intravascularly 2 min before alloxan in an 8:1 molar ratio of GSH:alloxan, delayed the onset of the permeability increase due to alloxan by 40-60 min but did not influence the maximum increase in permeability.5. Histamine administered intravascularly in concentrations from 0.02 to 0.50 mug/ml. perfusate had no significant effect on the alveolocapillary membrane permeability to [(131)I]albumin.