Effect of transitory ischemia on liver lysosomal apparatus in rats with different resistance to hypoxia.

We studied the state of lysosomal apparatus and pro- and antioxidant activity in the liver of rats with different resistance to hypoxia during postischemic recovery. Under normal conditions the lysosomal apparatus did not differ in highly and low resistant animals. During ischemia and reperfusion the damage to hepatic lysosomal membranes in rats highly resistant to hypoxia was less pronounced than in low resistant animals. These differences also concerned labilization of lysosomes during exposure to damaging factors (hypotonia and Triton X-100). The rats highly resistant to hypoxia differed from low resistant animals by higher stability of lysosomal membranes, lower prooxidant activity (malonic dialdehyde content), and higher tissue concentration of alpha-tocopherol during reperfusion.

Antioxidant properties, autooxidation, and mutagenic activity of echinochrome a compared with its etherified derivative.

Antioxidant properties of 2,3,5,7,8-pentahydroxy-6-ethyl-1,4-naphthoquinone (echinochrome A) were linked with the scavenging of peroxy radicals in liposomes, trapping of superoxide anion radicals, and binding of ferrous ions to inactive complexes in the aqueous phase. The antioxidant property of 6-ethyl-2,3,7-trimethoxy-5,8-dihydroxy-1,4-naphthoquinone (trimethoxyechinochrome A) was negligible. Autooxidation of echinochrome A was increased in basic media according to the degree of its dissociation. Autooxidation of polyvalent anions in basic media was accompanied by generation of naphthosemiquinone and superoxide anion radicals as free radical intermediates. An increased rate of echinochrome A autooxidation was noted in the presence of calcium ions. This was explained by a shift of pK of Ca2+-echinochrome A complexes toward acidic pH comparably with echinochrome A. Echinochrome A possessed pronounced mutagenic activity, while trimethoxyechinochrome A was inactive in the Salmonella/mammalian microsome reverse mutation assay (Ames test) for all examined cells (TA98, TA100, TA1537). Comparison of the chemical and biological activity of echinochrome A and trimethoxyechinochrome A demonstrated the key role of the beta-hydroxyl groups in the 2nd, 3rd, and 7th naphthol cycle positions. The O2-* and naphthosemiquinone radicals generated in the redox transition of 2,3-oxygroups may be the reason for the strongly pronounced mutagenicity of echinochrome A.