TRAM-34 (Triarylmethane-34) (Kd=20 nM), an effective and specific inhibitor of the intermediate-conductance Ca2+-activated K+ channel (IKCa1, KCa3.1), does not block cytochrome P450. The selective activity of TRAM-34(TRAM 34) is 200 to 1500-fold than other ion channels.

IKCa1:20 nM (Kd)

与克霉唑不同，TRAM-34选择性地抑制IKCa1，而不阻断细胞色素P450酶(CYP3A4)。TRAM-34在IKCa1转染的COS-7细胞中以及人类T淋巴细胞和T84细胞中的天然IKCa电流上，比克霉唑更强效地抑制克隆IKCa1通道。TRAM-34展现出对其他离子通道，如KV、BKCa、SKCa、Na+、CRAC和Cl-通道。TRAM-34显著地以295-910 nM和85-830 nM的IC50，分别抑制抗CD3 Ab或PKC激活剂PMA加钙离子载体离子霉素诱导的人类T淋巴细胞激活。5 μM的TRAM-34不影响人类T淋巴细胞或几种细胞线的细胞活力。[1] TRAM-34显著抑制EGF诱导的IKCa1上调，并以8 nM的IC50，抑制A7r5细胞的EGF刺激的增殖。[2] TRAM-34处理抑制人类子宫内膜癌(EC)细胞的增殖，并阻断EC细胞周期在G0/G1期。[3]

TRAM-34以约500-1,000倍于阻断剂量（0.5 mg/kg/day）的剂量连续治疗7天，对小鼠无毒性。[1] 以120 mg/kg/day的剂量给予TRAM-34能显著减少约40%的大鼠气球导管损伤（BCI）模型中的内膜增生。[2] 与其体外抑制EC细胞增殖的作用一致，30 μM的TRAM-34治疗能够减缓HEC-1-A肿瘤在体内的发展。[3]

Electrophysiology: The human IKCa1 is cloned and expressed in COS-7 cells. Cells are studied in the whole-cell configuration of the patch-clamp technique. The holding potential is 280 mV. The internal pipette solution contains: 145 mM K+ aspartate, 2 mM MgCl2, 10 mM Hepes, 10 mM K2EGTA, and 8.5 mM CaCl2 (1 μM free Ca2+), pH 7.2, 290-310 mOsm. To reduce currents from the native chloride channels in COS-7 cells, Na+ aspartate Ringer is used as an external solution: 160 mM Na+ aspartatey/4.5 mM KCl/2 mM CaCl2/1 mM MgCl2/5 mM Hepes, pH 7.4/290-310 mOsm. IKCa currents in COS-7 cells are elicited by 200-ms voltage ramps from -120 mV to 40 mV applied every 10 seconds and the reduction of slope conductance at -80 mV by TRAM-34 taken as a measure of channel block.

Cells are exposed to TRAM-34 for 48 hours. After 48 hours, cells are harvested by suction (suspension cells) or by trypsinization (adherent cell lines), centrifuged, resuspended in 0.5 mL PBS containing 1 μg/mL propidium iodide (PI), and red fluorescence measured on a FACScan flow cytometer. The percentage of dead cells is determined by their PI uptake, 104 cells of every sample being analyzed. (Only for Reference)