Effect of serum on the intracellular pH of BALB/c-3T3 cells: Serum deprivation causes changes in sensitivity of cells to serum

✍ Scribed by R. Martinez; R. J. Gillies; K. A. Giuliano

• Publisher: John Wiley and Sons
• Year: 1988
• Tongue: English
• Weight: 726 KB
• Volume: 136
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041360120

✦ Synopsis

One of the earliest responses of quiescent mammalian cells to the addition of serum is an increase in intracellular p H (pH'"). This pH'" change is generally believed to be due to an increased activity of Na'/Hf exchange. A number of investigators have observed steady-state differences in pH'" between cells in the presence and absence of serum. However, no one has examined differences in pH'" regulation that may exist between cells chronically exposed to, or deprived of serum. In this study, we investigated the effects of serum deprivation to identify those components of pH'" regulation that were associated with quiescence. To do this, we examined pH'" in cells growing chronically in 10% serum as well as in cells that were either acutely (1.5-2 hr) or chronically (48 hr) deprived of serum. lntracellular p H was monitored using the fluorescence of intracellularly loaded pyranine dye. Our results indicate that the resting pH'" values of chronically or acutely serum-deprived cells were not significantly different from each othcr yet, in both cases, were lower than those observed in cells exposed to 10% serum. Furthermore, we observed significant increases in pH"' of both acutely or chronically serum-deprived cells in response to the addition of serum at various concentrations, in the presence of 24 m M bicarbonate. Chronically serumdeprived cells had slightly smaller responses and were more sensitive to lower concentrations of serum than were acutely deprived cells. Therefore, our data suggest that long-term serum deprivation affects the magnitude and sensitivity of pH'" to serum stimulation and causes the loss of some form of pH'" regulatory mechanism(s).