MEASUREMENT OF INTRACELLULAR CALCIUM AND PH IN AVIAN NEURAL CREST CELLS

1. Intracellular pH (pHi) and calcium (Cai2+) were studied in freely migrating neural crest cells and in closely packed non‐migrating cells derived from avian neural tubes in vitro, using the fluorescent dyes 2,3‐dicyanohydroquinone (DCH) and Indo‐1 to measure pHi and Cai2+ respectively. 2. In freely migrating crest cells the pHi was approximately 0.2 pH units more alkaline and Cai2+ 90 nM lower than in closely packed cells. 3. Experiments to establish the cellular mechanisms regulating pHi in isolated neural crest cells demonstrate the presence of Na(+)‐H+ exchange in 66% of the cells and Na(+)‐HCO3(‐)‐dependent pHi‐regulating mechanisms in all cells examined. 4. Interactions between pHi and Cai2+ were examined. pHi was altered using either NH4Cl pulses resulting in small changes in Cai2+ or using a weak acid and base (propionate and trimethylamine), which produced a fall and a rise in Cai2+ respectively. 5. Exposure to Ca2(+)‐free media caused a lowering of Cai2+ and induced a transient acidification. 6. Application of BAPTA‐AM (50 microM), a cell‐permeant analogue of EGTA, resulted in a fall in Cai2+ and an intracellular acidification. 7. Co2+ and La3+ (2 mM) each induced a reversible fall in Cai2+ that was accompanied by intracellular acidification. These data suggest the presence of a transmembrane flux of Ca2+ in the resting cells. 8. It would appear that the mechanisms influencing Cai2+ and pHi are linked. This idea is discussed in terms of possible mechanisms and roles for Ca2+ and pH as modulators of neural crest cell behaviour. © 1990 The Physiological Society