 The compound has extremely high affinity to the open-form ryanodine receptor, a group of calcium channels found in skeletal muscle, smooth muscle, and heart muscle cells.It binds with such high affinity to the receptor that it was used as a label for the first purification of that class of ion channels and gave its name to it.At nanomolar concentrations, ryanodine locks the receptor in a half-open state, whereas it fully closes them at micromolar concentration.