Effect of alpha naphthylthiourea on uptake of 5-hydroxytryptamine from the pulmonary circulation.

Pulmonary injury caused by alpha naphthylthiourea (ANTU) is characterized by alterations of the capillary endothelial barrier followed by lung edema. Because pulmonary uptake of 5-hydroxytryptamine (5-HT) is dependent upon active transcellular transport by lung endothelium, it may be an index of early impairment of endothelial function caused by ANTU. We studied the effect of a single intraperitoneal dose of 5 or of 10 mg/kg of ANTU on pulmonary uptake of 5-HT by isolated rat lungs. Four h after the administration of ANTU, when lung tissue structure and dry-to-wet-weight ratios were comparable to those of control animals, 5-HT uptakes were significantly reduced (p < 0.05). Twenty-four h after the administration of ANTU, when lung edema was present on histologic examination and by lung weights, 5-HT uptakes were further reduced. They returned to control values 14 days after the administration of ANTU. Depression of 5-HT uptake is an early and reversible alteration of lung endothelial cell function caused by ANTU. Uptake of 5-HT may provide a sensitive probe with which to detect and evaluate pulmonary endothelial cell injury caused by toxicants.