A cytosolic pH fall is associated with the ATP depletion during hypoxia. Increase in cytosolic free Ca 2 + has also been hypothesized as an accelerating factor in the death of cells under hypoxia. To assess to what extent pH and Ca 2 + are involved in the cell death, we investigated the changes of these two parameters in muscle cells when applying a c hemical hypoxia . The cellular response to hypoxia beeing variable from cell to cell, measurements were performed at a single cell level. The myogenic precursors were satellite cells obtained from masseter muscle of normal adult pigs or from halothane susceptible (HS) pigs. These latter are known to carry a genetic mutation of the ryanodine receptor, the calcium channel of the sarcoplasmic reticulum, leading to abnormal cytosolic calcium regulation.Cells were grown until differentiation stage where spontaneous contractions occur. Hypoxia was induced by adding sodium cyanide and iodoacetate to a medium containing 1.8mM Ca 2 + or Ca 2 + -free. Fluorescence of the probes loaded in the cells, BCECF (for pHi) and Fura2 (for [Ca 2 + ]i), were recorded under dual wavelength excitation, every 2 min during 30 min at 37 o C.In all conditions, pHi fell abruptely within the first 10 min of hypoxia and then stabilises at a value of 6.5. This fall seemed to be more pronounced in normal cells. There was a transient and early increase of [Ca 2 + ]i in normal cells while [Ca 2 + ]i increased slowly and progressively in HS cells. Ultimate values of [Ca 2 + ]i were about the same for both type of cells. Blebs and subsequent cell death occured more frequently in normal cells than in HS. These results suggest that cell death may not be directly related to [Ca 2 + ]i increase. pH fall may be a determinant factor in cell injury leading to cell death.