Effect of propionyl carnitine on energy charge and adenine nucleotide content of cardiac endothelial cells during hypoxia.

Adenine mucleotide metabolism is very active in endothelial cells. These cells are very rich in xanthine oxidase which may produce oxygen reactive species during ischaemia and reperfusion when a high amount of adenine nucleotides may be catabolized to hypoxanthine. We investigated the effect of propionyl carnitine on energy charge and nucleotide content in cultured endothelial cells during changes in oxygen partial pressure. During hypoxia the adenine nucleotide pool and the energy charge decreased more slowly in the presence of 0.5 mM propionyl carnitine than in the absence of the compound. Furthermore during reoxygenation a more rapid increase of energy charge and adenine nucleotide concentration was observed with propionyl carnitine. These observations suggest that the presence of propionyl carnitine allows the endothelial cells to maintain their functionality and regulatory role on vessel activity for a longer time and decreases the formation of oxygen reactive species due to xanthine oxidase activity on hypoxanthine formed by adenine nucleotide catabolism.

Antidyslipaemic action and role of CoA in lipid metabolism of mitochondria and peroxisomes.

Our study has evaluated the effect of the parenteral administration of CoA on the pattern of haematic lipids and on palmitate oxidation in liver mitochondria and peroxisomes of rats made hyperlipaemic with a high fat diet with or without CoA. Lipid fractions, total cholesterol, triacylglycerols, total lipids and nonesterified fatty acids (NEFA) were determined in blood. Palmitate oxidation was determined in liver peroxisomes and mitochondria incubated in modified Krebs-Henseleit solution with 100 microM 1-14C palmitate in the presence and absence of some cofactors. Our results show that in rats fed with a high fat diet there was an increase of all lipid fractions. The increase of all lipid components was lower in animals treated with CoA. In liver peroxisomes of rats fed with high fat diet an increase in palmitate oxidation, that is higher when CoA is parenterally administered, was observed. In addition, palmitate oxidation in mitochondria of rats treated with CoA reached values higher than those of control and of rats fed with a high fat diet without CoA.

Protective effect of propionyl carnitine against peroxidative damage to arterial endothelium membranes.

Endothelial cells may be damaged by oxygen reactive species produced by granulocytes, by transition metal ions or by xanthine oxidase, an enzyme present in great quantity in these cells. Since it has been observed that propionyl carnitine protects the heart from peroxidation, we have investigated the effect of this compound on the formation of thiobarbituric acid reactive oxidation products (TBAR) in endothelial membranes. The peroxidation systems used were a mixture of Fe3+ and Fe2+, hydrogen peroxide and Fe2+, or xanthine oxidase-- xanthine. Propionyl carnitine at millimolar concentrations decreases TBAR formation. The protection is concentration-dependent and is almost absent in the presence of propionate and carnitine. From these results it appears that propionyl carnitine may protect not only myocardium but also vessels from peroxidative damage that occurs during ischaemia and reperfusion.

Metabolic fate of partially depolymerized chondroitin sulfate administered to the rat.

Partially depolymerized chondroitin sulfate (dCS) was tritiated and given to rats. With both the intramuscular and oral routes of administration the main route of excretion is urine. More than 40% of the radioactivity is present in tissues 24 h after administration. After intramuscular injection, radioactivity plasma levels rapidly increase with a peak at 0.6 h. The separation of the radioactive material on a Biogel P-4 column shows that the radioactivity in the first hour after injection is mainly constituted of dCS with molecular weight higher than 4000 daltons (dCS greater than 4000). The composition of the radioactive material changes with time; after 24 h the dCS greater than 4000 is a few percent of the total radioactivity. A large amount of tritiated water due to exchange and metabolization of dCS is found. Mono-, oligo- and polysaccharides resulting from the breakdown of dCS are also present. After oral administration, plasma radioactivity rapidly increases, with a shoulder and a small peak after 1 h and a large peak after 11 h. A tropism of the radioactivity towards glycosaminoglycan-rich tissues is observed. The presence of dCS greater than 4000 in plasma, synovia and cartilage after oral and intramuscular administrations of dCS may explain the chondroprotective effect of exogenous dCS. In fact, desulfated and sulfated oligo- and polysaccharides have regulatory effects on the synthesis and breakdown of hyaluronate-proteoglycan complexes of cartilage.

Cardiotoxic effects of adriamycin and mitochondrial oxidation in rat cardiac tissue.

Rats were subjected to chronic treatment with adriamycin (ADR). Significant alterations of ECG tracings were induced, starting from the third week of treatment. These alterations were related to mitochondrial damage of the heart tissue. A decrease of respiration rate in phosphorylating conditions was observed in isolated organelles over a period of three weeks. Meanwhile, adriamycinol (ADRol) concentration in heart extracts increased during chronic treatment.

Isolation of an urate-binding protein by affinity chromatography.

This paper describes an affinity chromatography procedure to purify an urate binding protein from human serum. The specific ligand was 8-amino-2,6-dihydroxypurine bound to Sepharose through the amino group. The specific elution was obtained with an uric acid or allopurinol solution. Electrophoretic analysis of the eluted protein shows a single sharp band with an α2-globulin mobility. Molecular weight, determined by gel filtration, is approximately 70,000 daltons.

The hepatotoxicity of thiobenzamide-S-oxide.

Administration of thiobenzamide (TB) (0.18 mmol/100 g b.w.) to rats caused the appearance in serum and urine of a compound identified as thiobenzamide-S-oxide. When synthesized and given by oral administration, this compound induced the early appearance of liver centrilobular necrosis, impairment of glucose-6-phosphatase and aminopyrine demethylase activities, and diminished cytochrome P-450 content. Liver necrosis was suppressed by the prior administration of 20-methylcholanthrene. It is concluded that TB-S-oxide is involved, possibly as a proximate precursor, in TB-induced liver damage.

Evidence of soluble proteins binding adriamycin by affinity chromatography.

The presence of various tissues of soluble proteins binding adriamycin is evidenced by affinity chromatography.

Affinity labeling of histidine and lysine residue in the adenosine deaminase substrate binding site.

1. Adenosine deaminase was inactivated by 9-(4-bromoacetamidobenzyl)-adenine (I) and 9-(2-bromoacetamidobenzyl)adenine (II), two affinity labels. 2. The stoichiometry of the reaction with reagent II is reported: 1 mol reagent is bound per mol inactive enzyme. Amino acid analysis of the 6 N HCl hydrolyzate of the inactive enzyme identified CM-histidine as the main alkylation product. This is the first evidence of the presence of a histidine in the active site region. 3. The alkylation rate and involved amino acid residues were studied for both reagents I and II, at pH 8 and 5.5. The particular reactivity of a lysine near or in the active site is discussed.

Effects of substituted 1,2,3-triazoles on adenosine deaminase, guanine deaminase and xanthine oxidase.

The action of some known and new synthesized substituted 1,2,3-triazoles on adenosine deaminase, guanine deaminase and xanthine oxidase was studied. The effect of substituents in 1, 4 and 5 positions was studied and discussed. The presence of a carboxamido group in 4 position seems to be essential in the binding to adenosine deaminase.

A powerful inhibitor of guanine deaminase.

The synthesis of 9-(p-carbetoxyphenyl) guanine is reported. The assays carried out on guanine deaminase from rat and rabbit liver and pig brain show that this compound is a powerful inhibitor. The compound has a Ki = 5 micronM for the enzyme from pig brain. The use of the inhibitor for the synthesis of a specific adsorbent for guanine deaminase was studied.