Effects of thiourea on pulmonary vascular permeability and on lung and plasma histamine levels in rats.

The intraperitoneal administration of thiourea (TU) to mature male rats results in a significant increase in lung vascular permeability to Evans Blue dye (EBD). On the other hand, young, sexually immature rats are resistant to this effect. The increase in lung vascular permeability in response to TU in mature rats is associated with corresponding increases in lung and plasma histamine levels. The correlation of increases in lung and plasma histamine in response to TU is similar to that reported for ammonium salts which produce similar pulmonary edema.