358 LIPID PEROXIDATION IN THE PATHOGENESIS OF HEPATOCYTE DEATH

G. Poll r E. Chiarpotto r F. Biasi, E. Albano r R. Carini, M.U. Dianzani

Department of Experimental Medicine and Oncology of the University,

Corso Raffaello 30, 10125 Torino, Italy.

The possible role of an increased peroxidative breakdown of biological membranes in the

achievement of irreversible liver cell damage by several toxic compounds has been investi-

gated using rat hepatocytes in single cell suspension. Hepatocyte suspensions have been

incubated up to 4-5 hours at 37°C in the presence or absence of carbon tetrachloride,

trichlorobromomethane, ferric or ferrous iron, ethanol. The drug concentration was suitably

adjusted to have significant cell death only after 2-3 hours incubation.

Under such experimental conditions the stimulation of membrane lipid peroxidation by the

studied compounds evaluated in terms of unpolar and medium polar aldehyde formation always

preceeded the evidence of irreversible hepatocyte changes, monitored by measuring cell lea-

kage of mitochondrial and cytosolic enzymes.

The strict dependence of the necrogenic activity of the toxic substances employed from

the oxidative stress by themselves produced has been demonstrated adding to the experimen-

tal system powerful antioxidants, namely vitamin E, vitamin A and promethazine. All these

compounds,showed to totally prevent the drug prooxidant effect, afforded a complete pro-

tection against hepatocyte death.

359 EFFECTS OF ETHANOL, GSH AND ETHANOL PLUS GSH ON HEPATIC MITOCHON- DRIAL MEMBRANES.

A.Ponces Freire*, M.J.Carrilho*, A.Freire**, P.Alves**, J.Pinto Correia** Biochemistry and Animal Physiology Center, Inst.Rocha Cabral*, Dept.Med.2 and Center GE (INIC),University Hospital Santa Maria**, Lisbon, Portugal.

Adducts formation between acetaldehyde and hepatic macromolecules has been pointed out as one possible mechanism for liver damage induced by ethanol. It has been shown in animal models that acetaldehyde dehydrogenase activity is decreased after ethanol in- take, specially in mitochondrial fraction. This is not verified when reduced glutathione (GSH) is added to the diet. Using monoamine oxidase (MAO) as mitochondrial outer membrane marker, the effect of ethanol, GSH and ethanol plus GSH on MAO kinetics was studied. 32 male Sprague-Dawley rats were fed four regimens (8 per regimen) during 30 days: standard diet and water ad libitum; standard diet and ethanol (6.1 g/Kg bw/day); standard diet and ethanol (6.0 g/Kg bw/day) plus GSH (0.39 n~nol/Kg bw/day); standard diet and GSH (0.49 mmol/Kg bw/day)

Km (raM) Substrate Control Ethanol Ethanol plus GSH GSH

Kynuramine (AB) 0.014 0.018 0.013 0.013 Benzylamine (B) 0.ii >0.5 0.12 0.19

Decreasing of MAO affinity for both substrates in animals that were fed an ethanol diet, may result from ethanol-induced mitochondrial membrane damage. Kinetic parameters on ani- mals fed ethanol plus GSH were similar to controls, suggesting a protective role for GSH.

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