Normal Ca2+ signalling in glutathione-depleted and dithiothreitol-treated HeLa cells

We have investigated whether reducing agents and substances that interfere with glutathione metabolism would affect the histamine-induced rises in internal Ca²⁺ concentration ([Ca²⁺]_i) in indo-1-loaded HeLa cells. Individual cells responded to 1 M histamine with either baseline or sinusoidal Ca²⁺ oscillations, a single Ca²⁺ peak or a maintained elevation of the [Ca²⁺]_i. Only a few cells did not respond. The sulphydryl reducing agent dithiothreitol (5 mM) did not affect these responses to histamine. A 24-h preincubation with 1 mM dl-buthionine (SR)-sulphoximine, which reduces the cellular glutathione content to less than 20% of its control value, affected neither these histamine responses, nor the [Ca²⁺]_i rises after application of 2 M thapsigargin. We conclude that oxidation of critical sulphydryl groups is not required for the normal response to histamine and also that glutathione plays no role in agonistinduced Ca²⁺ signalling in HeLa cells.