Thromboxane B2 (TxB2) metabolism in rat isolated lung and its inhibition by drugs.

In rat isolated lung perfused via the pulmonary circulation, 3H-TxB2 was metabolized to another radioactive species. About 60% of effluent 3H was metabolite and the same proportion of metabolite was found in lung at 5 min after the injection of 3H-TxB2. Metabolism of TxB2 was prevented by bromcresol green, dipyridamole and frusemide apparently by decreasing uptake of TxB2 by the lung. Our results support the possibility of TxB2 competing with PGE2 for metabolism in lung, although TxB2 is not a substrate for PGDH in vitro.