Role of the lungs in serotonin inactivation

Abstract

Isolated perfused rat lungs can inactivate small quantities (5–50 ng/ml) of serotonin (ST) almost completely. An increase in the ST concentration to 200 ng/ml and lengthening of the perfusion time weaken the ST inactivation. Cooling the lungs, or preliminary perfusion of the lungs with the addition of potassium cyanide (3·10−4 M), monoidoacetic acid (10−3 M), imipramine (10−5M), morphine (10−3 M), lysergic acid diethylamide (10−5 M), and cocaine (10−5 M) inhibit ST inactivation. The monoamine oxidase inhibitor iproniazid (10−4 M) does not affect the inactivation of ST by the lung tissue but increases the quantity of ST in it. It is postulated that the inactivation of ST by the lungs takes place in two stages: active uptake of ST by the lung cells from the perfusion fluid first, followed by its enzymic destruction.