A new technique to determine hydrogen excreted by gnotobiotic rats

A new system, that allowed the monitoring of hydrogen (H-2) excretion by gn otobiotic rats without affecting their defined microbial status, was develo ped. The system consists of an isolator containing a chamber for an experim ental animal, and a life-support system (LSS), with a sampling port outside the isolator connected to it. H-2 accumulation in the system was measured by analysing a defined volume of gas after removal. H-2 concentrations were determined with an electrochemical cell or by gas chromatography. To valid ate this technique, H-2 excretion by germ-free (GF) and mono-associated rat s fed a chemically defined diet was measured after oral application of lact ulose. Mono-associated rats had been obtained by colonizing GF rats with a H-2-producing Clostridium perfringens type A strain isolated from human fae ces of a healthy volunteer. Application of 50 mg lactulose to the monoassoc iated rats resulted in a significant increase in H-2 excretion. The net H-2 excretion was 7.82 +/- 1.28 ml H-2 in 12 h corresponding to a net maximal rate of 1.1 +/- 0.3 ml H-2/h. In contrast, in experiments with GF rats, les s than 0.13 ml H-2 were detectable within 12h. The technique presented is a useful tool for studying bacterial H-2 metabolism in vivo under gnotobioti c conditions.