Thromboxane B2 inhibits prostaglandin E2 inactivation by the rat isolated perfused lung.

1. The effect of thromboxane B2 (TxB2) on inactivation of prostaglandin E2 (PGE2) by the rat isolated perfused lung has been studied. 2. TxB2 when infused in low concentrations (100 ng/ml) into the pulmonary artery reduced PGE2 inactivation approximately two-fold. 3. The rat isolated fundus strip was contracted by higher concentrations of TxB2 (1.0 microgram/ml) in the presence of hyoscine, mepyramine, methysergide, phenoxybenzamine and propranolol. The size of contraction was reduced by indomethacin in concentrations known to inhibit prostaglandin synthetase. 4. Thus, in circumstances in which TxB2 and PGE2 are released concomitantly by the lung, low concentrations of TxB2 may augment PGE2 release by reducing its inactivation.