Blochrmicu et Blophysicu Actu 833 (1985) 119-127 Elsevier 119 BBA 51830 Effect of D-galactosamine in vitro on [U- l4 Clpalmitate oxidation, triacylglycerol synthesis and secretion in isolated hepatocytes Marise Mangeney, Olivier Sire, Jacqueline Montagne and Joseph Nordmann Luhorutoire de Biochlmie de lu Fucult~ de Mkdecine de Puris-Ouest et Groupe de Recherches (U 72) de I’INSERM, 45 rue des Saints-P&es, 75170 Paris cedex 06 (France) (Received December 7th, 1983) (Revised manuscript received September 21st, 1984) Key words: Triacylglycerol synthesis; Triacylglycerol secretion; D-Galactosamine; Palmitate oxidation; (Rat hepatocyte) zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJ Isolated rat hepatocytes were used to study in vitro effects of 10 mM D-galactosamine (GalN) on hepatic fatty acids metabolism. (1) At this concentration, membrane integrity and biochemical competence (i.e., gluconeogenesis and ureogenesis) remained unaffected. (2) Protein synthesis and secretion, as measured by the incorporation of [U-‘4C]leucine into total and medium protein, was significantly inhibited when incubated for more than 2 h. (3) GalN activated the incorporation of [U-14C]palmitate into triacylglycerols and depressed its utilization in the formation of lahelled ketone hodies and 14C0,. (4) Hepatocytes isolated from fasted rats exposed to GalN in vitro did not show any variation in prelahelled triacylglycerol secretion. (5) GalN induced a rapid inhibition of prelabelled triacylglycerol secretion by hepatocytes isolated from fed rats in which this secretion occurred to a larger extent than in hepatocytes isolated from fasted rats. The data reported here suggest that GalN induces a rise of triacylglycerol synthesis by inhibiting the palmitate oxidation pathway and a decrease of triacylglycerol secretion through an early derangement of the secretory pathway. Introduction It is well known that D-galactosamine (GalN) is an important model agent for studying the patho- genesis of liver injury. The biochemical mecha- nisms by which GalN exerts its toxic effects have been extensively studied in vivo [l-5]. Among other effects, a single dose of GalN produces a fatty accumulation within the first hours of intoxi- cation. In a previous study [6], we reported that palmitate oxidation was strongly decreased in hepatocytes isolated from rats injected 3 h before with GalN, this decrease being caused by an alter- ation of the palmitoylcarnitine transferase I (EC 2.3.1.21) activity [7]. In vivo studies with GalN have given ambiguous answers as to whether its effect is connected either with the protein synthe- &/secretion or free fatty acid afflux, or both [3,8-111. To avoid possible effects secondary to action on other organs, an in vitro model appears to be useful to study the effects of GalN on liver. Several investigators have described experimen- tal conditions where GalN induced in vitro bio- chemical perturbations in isolated hepatocytes similar to those observed in vivo, particularly in- hibition of glycogenolysis [12], uridine nucleotides depletion [13] and inhibition of protein synthesis [14]. The aim of the present study was to find out whether GalN in vitro could impair as well as in vivo long-chain fatty acid oxidation in isolated hepatocytes and to what extent this inhibition contributes to the triacylglycerol accumulation ob- served in vivo, since it has been well established that the oxidation and esterification pathways are 0005.2760/85/$03.30 0 1985 Elsevier Science Publishers B.V.