The inhibition of specific [3H]CFT binding (10nM) to membranes prepared from HEK 293 cells stably transfected with (•) wt (A), X-A90C (B), X-A135C (C), X-A306C (D), X-F319C (E), X-A342C (F), or with (○) X5C, resulting from a 2-min application of varying concentrations of MTSEA. The means and SEM of 3–6 independent experiments each performed with triplicate determinations are shown.