Beeler T J, Gable K
Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814.
J Membr Biol. 1993 Aug;135(2):109-18. doi: 10.1007/BF00231436.
The polycationic dyes, Hoechst 33342 (Bisbenzimide,2'-(4-ethoxyphenyl)-5-(4-methyl-1-piperazinyl)-2,5'-bi-1H- benzimidazole) and Hoechst 33258 (Bisbenzimide,2'-(4-hydroxyphenyl)-5-(4-methyl-1-piperazinyl)- 2,5'-bi-1H-benzimidazole) alter the activity of the sarcoplasmic reticulum Ca2+ channel. Although they act competitively, Hoechst 33342 decreases, while Hoechst 33258 increases, the rate of channel-mediated Ca2+ efflux from junctional sarcoplasmic reticulum vesicles. Unlike other cationic sarcoplasmic reticulum Ca2+ channel antagonists, Hoechst 33342 blocks the ryanodine-activated Ca2+ channel. Both Hoechst 33342 and Hoechst 33258 inhibit the channel incorporated into the planar lipid bilayer. Since the only structural difference between the two dyes is that the agonist Hoechst 33258 has a hydroxy group where the antagonist Hoechst 33342 has an ethoxy group, it is possible that the more hydrophobic, bulky ethoxy group blocks Ca2+ movement through the channel, whereas the hydroxy group only reduces the rate of Ca2+ movement.
聚阳离子染料Hoechst 33342（双苯并咪唑，2'-（4-乙氧基苯基）-5-（4-甲基-1-哌嗪基）-2,5'-联-1H-苯并咪唑）和Hoechst 33258（双苯并咪唑，2'-（4-羟基苯基）-5-（4-甲基-1-哌嗪基）-2,5'-联-1H-苯并咪唑）可改变肌浆网Ca2+通道的活性。尽管它们具有竞争性作用，但Hoechst 33342可降低，而Hoechst 33258可增加通道介导的Ca2+从连接肌浆网囊泡外流的速率。与其他阳离子肌浆网Ca2+通道拮抗剂不同，Hoechst 33342可阻断ryanodine激活的Ca2+通道。Hoechst 33342和Hoechst 33258均可抑制整合到平面脂质双分子层中的通道。由于这两种染料之间唯一的结构差异在于激动剂Hoechst 33258在拮抗剂Hoechst 33342具有乙氧基的位置有一个羟基，因此有可能疏水性更强、体积更大的乙氧基会阻断Ca2+通过通道的移动，而羟基仅降低Ca2+移动的速率。
