METABOLISM OF CYSTEINYL LEUKOTRIENES IN THE PERFUSED-RAT-LIVER - THE INFLUENCE OF ENDOTOXIN PRETREATMENT AND THE CELLULAR HYDRATION STATE

The influence of endotoxin on the hepatic metabolism and elimination o f H-3-leukotriene C-4 (LTC(4)) and 3H-leukotriene E(4) was studied in the single-pass perfused rat liver, Endotoxin (4 mg/kg body mass) was injected intraperitoneally 8 to 10 hours before livers were isolated f or perfusion, Tritiated leukotriene C-4 and leukotriene E(4) (10 nmol/ L) were infused for 5 minutes, and metabolites in bile were determined by high-pressure liquid chromatography. In livers without endotoxin p retreatment, single-pass uptake of LTC(4) was 77.3% +/- 3.2%, and 73.8 % +/- 1.8% of the radioactivity taken up was excreted into the bile wi thin 80 minutes, In endotoxin-pretreated livers, LTC(4) uptake was 62. 8% +/- 3.5% and only 31.2% +/- 1.5% of the radioactivity taken up was eliminated into the bile within 80 minutes, Bile how was reduced to 0. 20 +/- 0.07 mu L/g/min, compared with 1.18 +/- 0.18 mu L/g/min in untr eated livers. Biliary excretion of infused H-3-LTE(4) was also reduced in endotoxin-pretreated livers (31.5% +/- 6.1% compared with 61.4% +/ - 3.3% without endotoxin pretreatment), whereas uptake was not signifi cantly different. The effect of cellular hydration state on leukotrien e processing was also investigated. Anisoosmotic cell volume changes d id not influence uptake and biliary excretion of H-3-LTC(4) and its me tabolism in control livers. In endotoxin-pretreated livers, however, c ell swelling induced by hypotonic perfusion media (225 mOsm/L) or by 3 mmol/L glutamine increased biliary elimination of the radioactivity t aken up by 68% and 54%, respectively, Bile flow was also stimulated (0 .31 +/- 0.09 mu L/g/min and 0.46 +/- 0.01 mu L/g/min, respectively), C olchicine (5 mu mol/L) completely abolished the stimulatory effect of hypotonic perfusion on biliary leukotriene excretion, Hypertonic perfu sion decreased leukotriene elimination into bile to 18.1% +/- 3.8% of the radioactivity taken up and bile flow to 0.11 +/- 0.04 mu L/g/min. In livers perfused with hypertonic perfusion buffer, there was a highe r amount of polar omega-oxidation metabolites detectable in bile compa red with normotonic conditions. The data indicate that endotoxin impai rs the canalicular excretion of cysteinyl leukotrienes, whereas there is only minor influence on uptake and intracellular metabolism. Cell s welling increases the biliary elimination of cysteinyl leukotrienes in endotoxin-treated livers, whereas cell shrinkage has the opposite eff ect, suggesting a modulatory role of cell volume in the canalicular tr ansport of cysteinyl leukotrienes, at least in endotoxemia, Colchicine sensitivity of the cell volume effect suggests the involvement of a m icrotubule-dependent mechanism.