NORMAL CA2+ SIGNALING 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 muM 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 muM 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 agonist-induced Ca2+ signalling in HeLa cells.