ENDOTOXIN TOLERANCE AND POLYMYXIN-B MODIFY LIVER-DAMAGE AND CHOLESTASIS INDUCED BY A SINGLE DOSE OF ALPHA-NAPHTHYLISOTHIOCYANATE IN THE RAT

A single oral dose of alpha-naphthylisothiocyanate (ANIT) induces intrahepatic cholestasis and endotoxemia in the rat. To assess if a pathogenic relationship between endotoxin and ANIT-induced liver injury could be postulated, rats were pretreated by either induction of endotoxin tolerance, or with the anti-endotoxin agent polymyxin B. A single oral dose (10 or 20 mg/100 g body wt) of ANIT was then given to ascertain whether these methods of modifying endotoxicity would protect the animals against ANIT damage. Both pretreatments significantly reduced the incidence of endotoxemia after ANIT administration, as detected by either lead acetate enhancement method or the Limulus gelation test (LGT). The lethality of a single 20 mg/100 g body wt dose of ANIT was reduced from 55% to 15% by polymyxin B administration, and to 10% by an endotoxin-tolerant state. Moreover, when 10 mg/100 g body wt ANIT was given none of the animals died in 10 days, and the serum levels of bilirubin, alkaline phosphatase (AlPh), gamma-glutamyl transferase (gamma-GT), and transaminases (evaluated 1, 2, and 5 days after treatments) were significantly lower in the endotoxin-tolerant or polymyxin B administered rats; this biochemical protection was mirrored in the lack of histological alteration. The results demonstrate that the modification of endotoxicity offers significant protection against acute liver damage induced by ANIT. Thus the development of endotoxemia may play a pathogenic role in ANIT-induced liver injury. This conclusion is supportive of the hypothesis that endotoxins are necessary for the hepatotoxic agent to exert its full effects.