Figure 3: Effects of pepsin on cell survival, as measured by methylene blue absorption, and expressed as a % of absorbance of treatment with the corresponding pH without pepsin (control). Pepsin induced a significant decrease in cell survival independent of pH ( ; ). Data are expressed as means (histograms) and SEM (bars) for 3 replicates. See supplement Figure  1 for the effect of pepsin on cell survival of all the pH levels used in the statistical analysis.