UNIFORMLY C-14-LABELED PLANT-CELL WALLS - PRODUCTION, ANALYSIS AND BEHAVIOR IN RAT GASTROINTESTINAL-TRACT

Uniformly C-14-labelled primary cell walls (C-14-PCW) were purified from suspension-cultured cells of spinach (Spinacia oleracea L.) grown in a medium containing D-[U-C-14]glucose. The approximate polymer composition of the C-14-PCW preparation (% total C-14) was homogalacturonan 30, rhamnogalacturonan 23, xyloglucan 10, other hemicelluloses 3, cellulose 21, lignin 0, C-14-labelled protein < 3 and [C-14]starch < 2. The degree of methyl esterification of the pectic polysaccharides was about 25%. The C-14-PCW contained about 4% O-acetyl and 3% non-volatile ester-linked residues. When tracer levels of these C-14-PCW were fed to rats, only about 18% of the C-14 appeared in the faeces; negligible levels of C-14 (0-07%) remained in the gut contents 4 d after feeding. Some C-14 WaS present in the carcass. The results show that U-C-14-labelled primary cell walls can be purified and radiochemically analysed by the methods developed here, and that primary cell walls are extensively fermented by the gut microflora of the rat.