Fig. 1. Time course and dose dependence of 4-chloro- m -cresol (4-CmC)–induced intracellular Ca2+release. Dakiki cells in suspension bathed in Hanks balanced salt solution (HBSS) (A ), low-Ca2+HBSS ( B ), or Ca2+-free HBSS (C ). Traces show fura-2 ratios resulting from addition of 0.5, 1.0, 1.5, 2.0, or 2.5 mm 4-CmC at 30–50 s. Estimated intracellular Ca2+concentration for a fura-2 ratio of 5 was 206 nm. Dimethyl sulfoxide controls showed no effect on Ca2+release. ( D ) 4-CmC dose–response. Dakiki cells bathed in HBSS (▴), low-Ca2+HBSS (○), or Ca2+-free HBSS (•). Y values are the mean ± SEM of peak minus baseline fluorescence ratios for specified concentrations of 4-CmC. In HBSS, n = 3–6 for each concentration; in low-Ca2+HBSS, n = 3–10; in Ca2+-free HBSS, n = 5–23 for all concentrations except 1 mm 4-CmC, where n = 75.