SUMMARY

dine alkaloid, monocrotaline, and a pyrrole, dehydroretromecine, on the biochemical functions of the pulmonary endothelium. Mol. Pharmacol., 14, 1189-1203. Monocrotaline was placed in the drinking water of rats at a concentration of 20 mg per liter for periods of up to three weeks. This method of administration produced pulmonary arterial hypertension and right ventricular hypertrophy without inflammatory changes. No changes were noted in liver weight or RNA or protein synthesis in the liver. Isolated, perfused lungs from treated rats were examined for changes in four endothelial cell functions: angiotensin converting enzyme (E.C.3.4.99.3), 5’-mucleotidase (E.C.3. 1.3.5), serotonin uptake and metabolism, and norepinephrime uptake and metabolism. Mono-amine oxidase (E.C.1.4.3.4) is involved in the metabolism of both transmitters. The activities per lung of the 3 enzymes were unaltered. Norepinephrmme transport was also unaffected. Serotonim transport was specifically and markedly impaired. Extraction of serotonin from the perfusate was reduced to 33 % of control. Dehydroretronecine, a metabolite of monocrotaline, produced right ventricular hyper-trophy following daily subcutaneous administration for 2 weeks at a dose of 4 mg/kg