Influence of dietary carrageenans on microbial biotransformation activities in the cecum of rodents and on gastrointestinal immune status in the rat.

Rats, mice, and hamsters were fed iota-carrageenan incorporated in a fiber-free, purified diet for 30 days, and the activities of a number of cecal microbial enzymes were determined in vitro. Carrageenan treatment produced cecal enlargement in all species, yet significantly decreased the concentration of bacteria per gram of cecal content. Azoreductase, beta-glucosidase, beta-glucuronidase, nitrate reductase, and nitroreductase activities per gram of cecal content were significantly decreased in the rat, although less consistent effects were found in these enzymes in the mouse and hamster. beta-Glucuronidase and nitrate reductase functions were increased per gram of cecal contents in the hamster. The total activity per cecum of certain of these enzymes was modified by the concomitant cecal enlargement, yet total nitroreductase activity was significantly decreased in all three rodent species. iota-Carrageenan significantly decreased the concentration of enterobacteria, staphylococci, streptococci, lactobacilli, facultative anaerobes, and the total microscopic count in the rat cecum, but did not exert any effect on bacterial viability in vitro. Although having no effect on biliary IgA antibody concentration, iota- and kappa- carrageenan when present at 50 g/kg diet increased the agglutination response of the IgA specific for the hindgut microflora.