Intracellular pH changes during the cell cycle in Tetrahymena

Abstract

The equilibrium distribution of 5,5-dimethyloxazoladine 2,4-dione (DMO) between intra- and extracellular volume was used to estimate intracellular pH (pHi) in Tetrahymena pyiformis. In control experiments, DMO was found to equilibrate rapidly in response to a pH gradient. Under normal growth conditions, pHi was constant over a finite range of external pH, being maintained near pH 7.1 over the external pH range 5.2 to 7.3. This same range of external pH was also optimal for growth. pHi was monitored during the cell cycle of a synchronous population of T. pyriformis GL. The cells were synchronized either by starvation/refeeding or heat shock. Under both conditions, there were two alkaline shifts of approximately 0.4 pH units per cell cycle. These shifts in pH retained a constant remporal relationship to S phase and were not affected by changes in the time, duration, or magnitude of cytokinesis.

Observations on intracellular pH during cleavage of eggs of Xenopus laevis.

“…In the majority of our experiments, we were unable to detect any cycling of pH, with mitosis, and certainly nothing of the magnitude reported by Gerson and Burton (5) or Gillies and Deamer (6). In other experiments from this laboratory we were able to confirm a cycle of pH with mitosis in Physarum, although our values of pH; 7 .0-7 .4 with a peak just before mitosis differ considerably from the values reported by Gerson and Burton (M .…”

Regulation of intracellular pH in eukaryotic cells

“…Thus, small pH1 changes dramatically influence the responsiveness of such cells (Moody, 1984). Also, intercellular communication via gap junctions, which is important in development and in organized functioning of tissues, is highly sensitive to pH changes (Spray et al, 1982 (Gillies & Deamer, 1979). A single pH1 shift of similar magnitude has been reported in the slime mould Physarum polycephalum (Gerson & Burton, 1977).…”

The acidic microenvironment as a possible niche of dormant tumor cells

“…Extracellular acidity modulates intracellular pH that in turn directly affects cell cycle. This is a quite common mechanism for cell proliferation control in both normal and cancer cells that was demonstrated several years ago [29]. When internal pH drops following a sustained extracellular acidosis, also G2/M entry is limited by a reduced cyclin-dependent kinase 1-cyclin B1 activity [30].…”