Hypophagia-induced hypometabolism during experimental anaemia in rats

Several investigators have reported a drop in oxygen (O-2) consumption (Vo( 2)) and body temperature in laboratory animals during normobaric or hypobar ic hypoxia. Hypophagia, with normal efficiency of protein utilisation for g rowth, was also observed. It has recently also been observed that hypometab olism is present during anaemic hypoxia. The present study was designed to test the experimental hypothesis that anaemic hypoxia induces hypometabolis m secondary to hypophagia. Episodes of anaemia were created in adult male r ats by either blood withdrawal through cardiac puncture (haemorrhagic anaem ia) or phenylhydrazine administration (haemolytic anaemia). Haematrocrit, V o(2), and food consumption, as indirect estimations of the level of anaemia , energy production, and appetite, respectively, were serially measured in all animals during 7 days (acute experiments) or 17 days (chronic experimen ts). Positive correlations were found between the three parameters during d evelopment of and recovery from anaemia during each anaemic episode. When t he amount of food offered to non-anaemic rats was equalised to that freely eaten by anaemic rats, Vo(2) dropped in the former to almost the level foun d in the latter. Body composition changed during chronic anaemia because of a decrease in the lipid fraction of the body. The results confirmed the wo rking hypothesis that hypometabolism, which has been considered as an immed iate, emergency-type response to both hypoxic and anaemic hypoxia, can be c onsidered as a response secondary to hypophagia because of depressed appeti te. How appetite is adapted to the mechanisms which control O-2 convection and O-2 availability is not known at present.