查看文章

In this study, the presence of a bicarbonate gradient-dependent, carrier-mediated anion exchange process for butyrate (a representative short-chain fatty acid) uptake in apical membrane vesicles isolated from rat distal colon is described. An outward gradient of both butyrate- and bicarbonate-stimulated [¹⁴C]butyrate uptake and resulted in transient accumulation (an “overshoot”· phenomenon). Butyrate gradient-stimulated [¹⁴C]butyrate uptake was not altered either by an imposed pH gradient or at different pH values. In contrast, bicarbonate gradient-stimulated [¹⁴C]butyrate uptake was stimulated severalfold by an additional imposition of an outward pH gradient (pH_i = 7.5; pH₀ = 6.0). This bicarbonate- and pH gradient-stimulated butyrate uptake was not inhibited by either voltage clamping, with equimolar intravesicular and extravesicular K⁺ and valinomycin, or 4,4′-diisothiocyanatostilbene-2, 2′-disulfonic acid …