Redox Potential in Caecal Contents of the Rat and Azo Reduction of Salicyl-Azo-Sulphapyridine

Abstract

1. Redox potentials were measured in the caecum of ambulant rats, anaesthetized rats and in vitro in the caecal contents of rats, mice, guinea-pigs and rabbits. The potentials recorded ranged from —100 to —400 mV with small differences between the various sets of experiments.

2. The rate of azo reduction of salicyl-azo-sulphapyridine in rat caecal contents was the same in vivo as in vitro, mean azo half-life (t_0·5) was 10·8 min in both sets of experiments.

3. The rate of azo reduction of salicyl-azo-sulphapyridine in caecal contents, as measured in vitro, was most rapid for rabbits (t_0·5 = 3·5 min), intermediate for rats (t_0·5 = 10·8 min), and slowest for mice and guinea-pigs (t_0·5 = 15·1 and 17·6 min, respectively).

4. The presence of bacteria and a low redox potential (< — 100 mV) seemed to be prerequisites for azo reduction to take place.