The relation between L‐methionine uptake and sodium in rat small intestine in vitro

Abstract
1. Uptakes of L‐methionine and mannitol by rat jejunum in vitro were measured over test periods from 5 to 120 sec after 30 min pre‐test periods in the presence or absence of Na.2. The initial stage in methionine uptake was dependent on the presence of Na+ and to a lesser extent on the K+ concentration. In contrast mannitol uptake was independent of Na and K.3. The initial stage in methionine uptake can be reactivated 30–60% within 5 sec by replacing an Na‐deficient intestine into an Na‐containing medium.4. Initial methionine uptake was greater with a normal intracellular and low medium Na concentration than with a high medium and low intracellular Na concentration. It is suggested that the intracellular Na concentration is a critical factor, more important than the Na gradient, in determining the rate of amino acid transfer across the luminal membrane.

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