Exchange of cellular ³⁶Cl⁻ for extracellular Cl⁻ or Br⁻, but not for NO₃⁻, HCO₃⁻, or formate. Cells (sul1) were grown in LCAPG and incubated 2 h, 30°C, in fresh LCAPG + 8 μM Na³⁶Cl. Cells were centrifuged and resuspended at 30°C in LCAPG plus 2 mM KCl, KBr, K-formate, KNO₃, or KHCO₃, as indicated. Cellular ³⁶Cl⁻ as a percent of the value at the first time point is plotted on a logarithmic scale as a function of time. Unless otherwise indicated, the effluxes were performed in media buffered at pH 4.5 with 5 mM K-citrate. The two experiments at pH 6.0 were in media buffered with 5 mM K-citrate and 10 mM bistris. The semi-log plots are fit with straight lines because the time points are too early to reflect the slow component shown in Fig. 5.