In vitro exposure of rabbit tracheal epithelium to SO(2): Effects on morphology and ciliary beating

The aim of this in vitro study was to characterize the direct effects of short-term exposure to low concentrations of sulfur dioxide (SO(2)) on both the morphology and the physiology of rabbit tracheal primary cultures. Scanning electron microscopy (SEM) studies revealed that ciliated cells exposed for 1 hr to 10 ppm or 30 ppm SO(2) exhibited aggregated cilia. Transmission electron microscopy revealed numerous swollen mitochondria in cells exposed to 30 ppm SO(2) for 1 hr. This morphological damage to cells was coupled with physiological alterations. A 25% decrease in ciliary beat frequency (CBF) was measured in cells exposed to 30 ppm SO(2). This inhibition was partially reversible within 24 hr. This SO(2) concentration also induced a significant depletion of cellular ATP content which was completely restored after a 24-hr recovery period. A correlation was found between cellular ATP level depletion and CBF decrease.