The role of carbon dioxide in the metabolism of adultHaemonchus contortus, in vitro

Abstract

SummaryAdultHaemonchus contortusworms simultaneously excrete and fix CO2. Their initial content of CO2was measured as 4·55 μmoles/100mg wet weight and their excretion rate in air as 1 μmole/100 mg wet weight/h for at least 4 h. When the worms were incubated either aerobically or anaerobically with14CO2most of the metabolized radioactivity was associated with propan-1-ol and propionate but small amounts were found in succinate and lactate. No radioactivity was associated with ethanol or acetate, two major catabolites of glucose. Stepwise degradation of the metabolized radioactive propanol and propionate showed that all the radioactivity in both compounds was associated with carbon atom no. 1. These results show thatH. contortushas much in common with the anaerobic energy metabolism ofAscaris lumbricoidesbut they are not inconsistent with the utilization of the tricarboxylic acid cycle by the worm.H. contortusworms were found to metabolize their excretory products. When they were incubated with either [2,3-14C]succinate or [2-14C]acetate,14CO2was excreted under aerobic but not under anaerobic conditions. These results are consistent with a pathway similar to that used byAscarisoperating alone under anaerobic conditions and together with the tricarboxylic acid cycle under aerobic conditions.