Transport of Methionine Hydroxy Analog across the Brush Border Membrane of Rat Jejunum

摘要: Brush border membrane vesicles and everted rings of rat jejunum were used to study the absorption 2-hydroxy-4-methylthiobutyric acid, alpha-hydroxy analog methionine (DL-MHA). Uptake by was found be unaltered an inwardly directed sodium gradient in contrast that L-methionine, D-methionine L-lactate, which is stimulated exhibits a characteristic "overshoot" phenomenon. Initial uptake rates both L- (0.77 mM) respectively 6.8 1.5 times higher than DL-MHA (0.80 under Na+-gradient conditions. However, hydroxy significantly inhibited L-lactate accumulation into vesicles. jejunal sum saturable Michaelian component [KappM = 4.4 mM Vappmax 587 nmol/(g X min)] diffusive [Kd 47 microL/(g min)]. Furthermore, completely carrier-mediated DL-MHA. All this demonstrates mediated Na+-independent carrier system associated with transport thus quite distinct from L-methionine pathway. This difference could help explain numerous findings respect lower biological utilization some species when fed as sole source purified crystalline amino acid diets.