The protecting effect of L-carnitine on Ca(2+)-loaded rat liver mitochondria

Mitochondrial dysfunction in ischaemia-reperfusion

The mitochondrial dysfunction in ischaemia-reperfusion is shortly reviewed. During ischaemia the ATP level and pH drops, phospholipids are degraded, membrane permeabilities increased and the cytosolic levels of Na+ and Ca2+ raised. During the following reperfusion the Ca2+ levels may further increase while pH is raised. The oxidative phosphorylation is resumed and the ATP used for membrane repair and ion pumping. The mitochondrial Ca2+ handling is important in removing Ca2+ from the cytosol since the mitochondria are able to take up substantial amounts of Ca2+. However, if a certain threshold is exceeded, mitochondria undergo a so-called permeability transition (MPT), release their Ca2+, undergo swelling and become uncoupled. MPT has been shown to be due to the opening of large pore allowing passage of substances with a M(R) < 1500. Data are presented showing by electron microscopy swelling of mitochondria in cells in perfused liver before other gross morphological changes have taken place. There are a number of factors lowering the threshold for Ca2+ in inducing the MPT: inorganic phosphate, pro-oxidants that oxidize membrane SH-groups, oxidation of NAD(P)H and GSH, while a protective effect is exerted by Mg2+, ADP (and ATP), some antioxidants, carnitine, decrease in pH, and cyclosporin A that binds to cyclophilin. The potential benefit of these in minimizing reperfusion-induced tissue damage is discussed.

Dietary iron deficiency in the rat. I. Abnormalities in energy metabolism of the hepatic tissue

Severe iron deficiency was induced in rats by rearing nursing dams and their offspring on a diet comprising all the requisite nutrients and trace metals except iron. The iron deficient 5-week-old rats exhibited a severe anemia and a drastic decrease in iron content of the hepatic tissue and of the mitochondrial fraction. Cytochromes c + c1 and b were moderately but significantly reduced. A large increase in liver concentration was observed in iron-deficient animals; whereas there was no modification in total lipid, cholesterol, phospholipid and fatty acid composition of the mitochondrial membrane. Mitochondria from iron-deficient rats presented a partial uncoupling of the oxidative phosphorylation process. This functional derangement was completely reversed by the presence of either bovine serum albumin or L-carnitine plus ATP. This behaviour suggested that endogenous long-chain fatty acids could be primarily involved in the onset of mitochondrial dysfunction. The hepatic energy state of the liver appeared dramatically decreased under the pathological condition of severe iron-deficiency anemia. The possibility of a direct link between the partial loss of coupled functions observed in isolated mitochondria and the heavy energy deficit detected in the liver is discussed.