Thapsigargin, derived from the plant genus Thapsia^1,2, is an extremely tight-binding inhibitor of intracellular Ca²⁺ pumps. It was initially described as a tumor promoting agent that induces rapid Ca²⁺ release from intracellular stores³ by the inhibition of the sarcoplasmic endoplasmic reticulm Ca²⁺-dependent ATPase pump without inositol phosphate formation⁴. Thapsigargin-induced depletion of Ca²⁺ stores causes apoptosis in most cell lines⁵. It has also been shown to cause histamine secretion from rat mast cells⁶ and to stimulate arachidonic acid metabolism in macrophages⁷. Its tumour-promoting function probably results, at least partly, from cytotoxicity, causing a wound response in the skin⁸.

Thapsigargin Epoxide is a non-active analogue of Thapsigargin and can be used as a negative control for Thapsigargin activity^9,10.