In vivo31 P-NMR analysis of the effect of osmotic shock on phosphorylated metabolites in Dictyostelium cells (A) The experiments were performed as described for the determination of cytosolic pH by 31P-NMR using MEP as probe. Only the spectral region (+5 to -20 ppm) corresponding to phosphorylated metabolites is shown. (B) Temporal evolution of intracellular nucleoside di- and triphosphate content during hyperosmotic shock in Dictyostelium cells. The relative intracellular NTP content was calculated from the area of the P-NTP peak at about -20 ppm and the NDP content was deduced from the area of the (β-NDP + γNTP) peak at about -5 ppm. The NTP and NDP content (nmol/107 cells) before hyperosmotic shock (values at T = 0) were measured on perchloric acid extracts. Abb.: PME, phosphomonoesters; PDE, phosphodiesters; cytPi, extPi, cytosolic and extracellular Pi; NTP, NDP, nucleoside tri- and diphosphate; IP6, inositol hexakisphosphate.