Fermentation and subsequent disposition of 14C-labelled plant cell wall material in the rat

A 14C-labelled plant cell wall preparation (14C-PCW) produced from spinach (Spinacia oleracea L.) cell culture exhibits uniform labelling of the major polysaccharide groups (%): pectins 53, hemicellulose 13, cellulose 21, starch 3. This 14C-PCW preparation has been used in rat studies as a marker for plant cell wall metabolism. Metabolism of the 14C-PCW occurred largely over the first 24 h. This was due to fermentation in the caecum. The pectic fraction of the plant cell walls was degraded completely in the rat gastrointestinal tract, but some [14C]cellulose was still detected after 24 h in the colon. Of the 14C, 22% was recovered in the host liver, adipose tissue and skin, 26% excreted as 14CO2 and up to 18% was excreted in the faeces. There was no urinary excretion of 14C. In vitro fermentation using a caecal inoculum showed reduced 14CO2 production, 12% compared with 26% in the intact rat. 14C-PCW is a useful marker to investigate the fate of plant cell wall materials in the gastrointestinal tract. These studies show both bacterial fermentation of the 14C-PCW and host metabolism of the 14C-labelled fermentation products.