Ruthenium red

The inorganic dye ammoniated ruthenium oxychloride, also known as Ruthenium Red, is used in histology to stain aldehyde fixed mucopolysaccharides.

Ruthenium Red has also been used as a pharmacological tool to study specific cellular mechanisms. Selectivity is a significant issue in such studies as Ruthenium Red is known to interact with a large number of proteins. These include mammalian ion channels (CatSper1, TASK, RyR1, RyR2, RyR3, TRPM6, TRPM8, TRPV1, TRPV2, TRPV3, TRPV4, TRPV5, TRPV6, TRPA1, mCa1, mCa2), a plant ion channel, Ca2+-ATPase, mitochondrial Ca2+ uniporter, tubulin, myosin light-chain phosphatase, and Ca2+ binding proteins such as calmodulin. It should be further noted that Ruthenium red displays nanomolar potency against several of its binding partners (e.g. TRPV4, Ryanodine receptors,...). For example, it is a potent inhibitor of intracellular calcium release by Ryanodine receptors (Kd ~20 nM).