Digestion of native collagen in the gut

The digestion and absorption of collagen, native and artificially cross-linked, has been examined in the rat and the Gaboon viper, by feeding known quantities and measuring the hydroxy-proline content of the faeces and of the contents of the gut at different levels, and comparing with an unabsorbable marker (polyethylene glycol). Incubation of collagen in vitro with pepsin at 37 degrees C at pH 1.5 followed by trypsin or chymotrypsin converted about 40% into dialysable material.