FIG. 2.

Dose-dependent effects of GPFX (closed circles), CPFX (closed triangles), erythromycin (open squares), ampicillin (closed squares), and cefotaxime (open triangles) on the transepithelial PD. Increasing concentrations of the drugs were added to the superfusing solution, and the plateau PD value in response to each dose was determined. Values are expressed as decreases in the PD from the baseline value. Data are means ± SE; n = 9 for each point. The symbols * (P < 0.05) and ** (P < 0.01) indicate values that are significantly different from the baseline values.