LEUKOTRIENE D-4 ACTIVATES A CHLORIDE CONDUCTANCE IN HEPATOCYTES FROM LIPOPOLYSACCHARIDE-TREATED RATS

Endotoxin (LPS) can cause hepatocellular injury under several circumst ances, and leukotrienes have been implicated as a contributing factor. Since ion channel activation has been associated with cytotoxicity, t he aim of this study was to determine the circumstances under which LP S and/or leukotrienes activate ionic conductances in hepatocytes. LPS treatment of rats increased Cl- conductance in hepatocytes from 232+/- 42 to 1236+/-134 pS/pF. Voltage dependence and inhibitor specificity o f this conductance were similar to that of a swelling-activated Cl- co nductance, and internal dialysis with nucleoside analogues suggested c ontrol by an inhibitory G protein. The lipoxygenase inhibitor nordihyd roguaiaretic acid, the specific leukotriene D-4 (LTD4) receptor antago nist MK-571, and the 5-lipoxygenase activating protein inhibitor MK-88 6 all significantly inhibited the conductance. Intracellular dialysis with LTD4 (1.5 mu M) elevated intracellular Ca2+ from 143+/-6.5 to 388 +/-114 nM within 6 min and stimulated an outwardly rectifying conducta nce from 642+/-159 to 1669+/-224 pS/pF (n = 9, P < 0.001). In hepatocy tes prepared from untreated rats, this concentration of intracellular LTD4 neither raised intracellular Ca2+ nor activated the conductance. The LTD4 response could be induced in normal hepatocytes by culture wi th either conditioned medium from LPS-treated macrophages or purified TNF-alpha. In conclusion, intracellular LTD4 activates a chloride cond uctance in hepatocytes isolated from rats treated with LPS or primed i n vitro with TNF-alpha. Changes in the hepatocellular accumulation of leukotrienes therefore mediate channel activation and may contribute t o liver injury during sepsis and other inflammatory conditions.