Pulmonary clearance of tracers with different lipid and water solubility in experimental surfactant dysfunction

We measured the pulmonary clearance of inhaled 99mTc-diethylenetriamine penta-acetic acid (DTPA), 99mTc-sestamibi and 99mTc-dimethyliminodiacetic acid (HIDA) in normal rabbits, and rabbits with surfactant dysfunction induced by the detergent dioctyl sodium sulfosuccinate. The tracers differ widely in lipid/water partition coefficients, but have similar molecular radius and weight. Five animals in each group received the detergent in aerosol, and the other five a vehicle aerosol, before the administration of the tracer. Pulmonary clearance of the tracers was measured with a gamma camera. The half-life of 99mTc-DTPA was 94 +/- 16 min in normal lungs, and 10 +/- 1 min after detergent administration (p < 0.001). The half-life for 99mTc-sestamibi was 45 +/- 4 min and 39 +/- 4 min, respectively, (p < 0.05). There was no significant difference between the half-life of 99mTc-HIDA in normal lungs and in lungs with surfactant dysfunction. The half-life was 20 +/- 3 min and 17 +/- 2 min, respectively. The results indicate that the clearance rate limiting factors for the alveolocapillary transfer of water and lipid soluble substances are not the same. Surfactant dysfunction affects the transfer of water soluble substances (99mTc-DTPA) but not of substances with high lipid solubility (99mTc-HIDA).

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