Epithelial shedding is a characteristic feature of asthmatic airways and has been attributed to eosinophil products. We have examined the interaction of purified intraperitoneal guinea pig eosinophils with or without platelet-activating factor (PAF, 10(-7) M) or lyso-PAF (10(-7) M) with guinea pig tracheal epithelium in vitro. At 0, 4, 14, and 24 h, the percentage of ciliation of the tracheal circumference (CTC) was measured by light microscopy and the ciliary beat frequency (CBF) by photometry. PAF-activated eosinophils (50 x 10(6) cells/ml) disrupted the epithelium, mean CBF and CTC being reduced by 77.8 +/- 5.8% (mean +/- SEM; P less than 0.001 versus control) and 94.2 +/- 1.4% (P less than 0.001) over 24 h, respectively. PAF (10(-7) M) alone had no significant effect. Lyso-PAF with eosinophils (50 x 10(6) cells/ml) also reduced mean CBF and CTC but to a lesser extent. Eosinophils alone also led to a reduction of 36.2 +/- 11.4% in mean CBF and 53.0 +/- 15.5% in CTC, but these changes were not significant. The PAF antagonist, WEB 2086 (10(-6) M), significantly inhibited the mean CBF and CTC reduction due to PAF-activated eosinophils by 61.5 +/- 17.2% (P less than 0.01) and 20.8 +/- 6.5% (P less than 0.05), respectively. In addition, catalase (1,125 U/ml) partially inhibited the mean CBF and CTC reduction induced by PAF-activated eosinophils. Intraperitoneal neutrophils (PMN) (50 x 10(6) cells/ml) also disrupted epithelium but to a lesser extent (24-h reduction: 34.2 +/- 12.7% for mean CBF and 60.2 +/- 13.2% for CTC, respectively). Stimulation with PAF (10(-7) M) had no further effect. Marked exfoliation of the epithelial layer was observed after 14 h of incubation with activated eosinophils. We concluded the PAF-activated eosinophils are capable of grossly disrupting ciliated epithelium and may contribute to epithelial damage observed in asthma.