Absorption of methionine and methionine sulphoxide in rat intestine and the effect of glutathione.

The absorption of methionine and methionine sulphoxide was compared in inverted rings from three sections of rat intestine. In all sections, absorption of unoxidized methionine was 20-40% higher than that of methionine at low physiological substrate concentrations. At higher substrate levels, the difference was not so pronounced. Inhibition studies indicated that absorption of methionine and of methionine sulphoxide took place by different absorption systems. Glutathione increased the absorption of methionine and, to a greater extent, the absorption of methionine sulphoxide.