FIGURE 4.

Trans-stimulation of hCAT-2/A14_BK in comparison with hCAT-1 and hCAT-2A. Xenopus oocytes expressing the indicated transporters were incubated in amino acid-free medium for 4–6 h and then injected with 36 nl of 100 mm l-[³H]arginine (100 μCi/ml). Three oocytes each were incubated for 30 min in pH 7.5 buffer containing either no amino acids or 1 mm arginine. Subsequently, the radioactivity in the supernatants was determined. Values obtained with non-injected oocytes were subtracted, and the radioactivity in buffer containing no amino acids is expressed as a percentage of the respective radioactivity detected in the extracellular buffer containing 1 mm l-arginine (100%, dashed line). Bars represent means ± S.E. (n = 9–15), with at least three different batches of oocytes. Statistical analysis was performed using analysis of variance with the Bonferroni post hoc test. ***, p ≤ 0.001; n.s., not significant.