We have measured the pH of Dictyostelium discoideum cells using the pH-dependent fluorescence of intracellularly trapped fluorescein. The pH of cells measured 45 minutes after initiation of differentiation by starvation is between 6.2 and 6.3 (6.23,+/-0.1). At approx. 2 hours into differentiation cells undergo a rapid, transient intracellular alkalinisation during which the pHi rises to 7.13 (+/-0.3,n=4). By 20 min. later the pHi has returned to the original value (6.2-6.4). This increase in pHi can be inhibited by several treatments which also delay the differentiation program. Cells which are removed from growth medium but are incubated in medium containing 3% dextrose do not exhibit this transient increase in Phi. Differentiation in Na-free or in amiloride-containing solutions can also prevent the alkalinization event from occurring and suggest that the alkalinization is Na-dependent and similar to the Na+/H+ exchange mechanism that has been studied in other cell types. When the alkalinization is prevented by amiloride treatment, cells do not progress normally into differentiation. The transient alkalinization appears to be temporally associated with other differentiation-related cellular processes in Dictyostelium and may be related to the acquisition of cellular 'memory' or commitment to the developmental program since after 2 hrs an 'erasure' period is required before cells revert to a vegetative phenotype.
|Pages (from-to)||no. 2190|
|State||Published - Jan 1 1984|