Fig. 2. Effects of various stresses on pH_i homeostasis. pH_i was measured in wild-type cells treated as described in Materials and Methods. pH_i after heat shock, cold shock, hyper-osmotic shock, and hypo-osmotic shock were measured at t=1 hour, whereas pH_i after high density incubation was measured at t=3 hours. pH_i measurements after all other stresses were made within 12 minutes of the insult. n ranges from 20 to 40.