Effects of Cysteamine ∗ and Cysteine on Cardiac Output and Oxygen Content of Venous Blood

Abstract

Summary and Conclusions

Data are submitted concerning the changes in cardiac output, systolic output, pulmonary ventilation, oxygen consumption, and oxygen content of the mixed venous blood of the right heart following intravenous administration in anesthetized dogs, of 2 radioprotectors, cysteine and cysteamine. 1. Cysteamine (= β-mer-captoethylamine = Becaptan Labaz), for doses of 10-40 mg/kg, generally increases the cardiac output and the systolic output from 10 to 75% of control values. Heart rate and femoral blood pressure are unaffected. No significant change is noted in the oxygen content of the mixed venous blood. 2. The effects of cysteine are as follows: a) For doses of 20-80 mg/kg, the cardiac and systolic outputs do not change significantly; blood pressure, heart rate, and oxygen blood content remain at control values, b) Doses of 320 mg/kg in 2 of 3 dogs induce a large decrease in both cardiac output and stroke volume. In all cases, the oxygen content of the mixed venous blood is reduced, most conspicuously 5 minutes after the injection. 3. Equiprotective doses of cysteamine do not decrease the oxygen content of the mixed venous blood. 4. It is concluded: a) that the remarkable protection afforded against X-rays by β-mercaptoethylamine is not due to tissular anoxia, b) that the temporary anoxia produced by large doses of cysteine can explain only partially the radioprotective action of the substance.