Voltage-dependent K^＋-channel Responses during Activation and Damage in Alveolar Macrophages Induced by Quartz Particles

The roles of voltage-dependent K^＋ channels during activation and damage in alveolar macrophages （AMs） exposed to different silica particles were examined. Rat AMs were collected by means of bronchoalveolar lavage, and were adjusted to 5× 10^5/mL. After AMs were exposed to different concentrations （0, 25, 50, 100, 200 μg/mL） of quartz particles and 100 μg/mL amorphous silica particles for 24 h, the voltage-depended K^＋ current in AMs was measured by using patch clamp technique. Meanwhile the leakage of lactate dehydrogenase （LDH） and the viability of AMs were detected respectively. Patch clamp studies demonstrated that AMs possessed outward delayed and inward rectifying K^＋ current. Exposure to quartz particles increased the outward delayed K^＋ current but it had no effect on inward rectifier K^＋ current in AMs. Neither of the two K^＋ channels in AMs was affected by amorphous silica particles. Cytotoxicity test showed that both silica particles could damage AM membrane and result in significant leakage of LDH （P〈0.05）. MTT studies, however, showed that only quartz particles reduced viability of AMs （P〈0.05）. It is concluded that quartz parti- cles can activate the outward delayed K^＋ channel in AMs, which may act as an activating signal in AMs to initiate an inflammatory response during damage and necrosis in AMs induced by exposure to quartz particle. K^＋ channels do not contribute to the membrane damage of AMs.