Effects of iron, ascorbate, and α-tocopherol on liposomal lipid peroxidation

Effects of iron, ascorbate, and α-tocopherol on liposomal lipid peroxidation

J Mol 112 Cell Cardiol Possible 20 (Supplement Tolerance Factor on Glucose Transport in Isolated Rat Cardiomyocytes Y. Fischer. H. Rose & H. Kam...

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J Mol

112

Cell

Cardiol

Possible

20 (Supplement

Tolerance Factor on Glucose Transport in Isolated Rat Cardiomyocytes Y. Fischer. H. Rose & H. Kammermeier Department of Physiology, Med. Fat. RWTH Aachen. Pauwelsstr. 5100 Aachen, FRG A cationic glucose tolerance factor (GTF) was partially purified from commercially available yeast extract by butanoi extraction, dialysis and ion exchange chrbrkatography as previously bescribed. GTF was reported by others to stimulate 3-O-Methyl-Glucose and D-glucose uptake by rat adipocytes. The fractions found to have a GTF activitv. as measured bv the stimulation of U-14C-Dglucose uptake in isolated rat cpididymal adipocytes, were tested on resting isolated, Ca-resistent rat cardiomyocytes. To this end. the cells were incubated with 2-deoxy-D-(l-3H)-qlucose (DOG) at tracer concentiations (1.4 pM or less) and the uptake of the sugar was measured ekher under basal conditions (no addition) or in the presence of different dilutions of the fractions with GTF activity. These fractions did stimulate DOG uptake by cardiomyocytes up to two-fold as compared to basal values. This effect was in part masked in the strong cationic fractions by a DOG-uptake-inhibiting-component that was shown to be distinct from (a) GTF activity bearing subtancetsl. As other authors could not detect more than one cationic GTF after further purification from yeast extract and as the dose-response relationship we found for GTF activity was similar in adipocytes and cardiomyocytes. the observed stimulating action of the investigated fractions on cardiomyocytescould possibly be accounted for by GTF. (supported

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113POTENTIAL ROLE OF ENDOTHELIUM-DERIVED RELAXING FACTOR IN THE PROTECTION AGAINST FREE RADICAL INJURY. of G .M. Rubanyi , Department Pharmacology, Berlex Laboratories, Inc., Cedar Knolls, U.S.A. Oxygen-derived free radicals play an important role in the pathogenesis of various diseases. Recent studies indicated a close relationshio between oxvaen-radicals and the Dotent vasodilator endothel i umlderived relixi ng factor (EDRF) : (i ) superoxide anion (* 0 -) inactives EDRF and (ii) hydrogen peroxide (H 02)and hydroxyl radfcal (*OH) stimula;e the synthesis/release of EDR8. If EDRF is (in the course of inactivation by this able to eliminate *O,radical ) , it’s incressed production by Hz02 and/or OH may serve as an important protectiv_e mechanism. We tested the hypothesis that EDRF is EDRF (released from perfused doq a free radical (*O, ) scavenaer. aorta) and authentfc.nitric oxide (NO) (believed to be’one of theEDRF’s.1 significantly depressed reduction of cytochrome 4 in response to a0 generated by the xanthine oxidase + xanthine reaction or by activ E ted human neutrophils. EDRF and NO had no direct effect on These data indicate that EDRF (NO) can “scavenge” * O,cvtochrome c. and therefore may provide protection against free radical injury. L

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EFFECTS OF IRON, ASCORBATE, AND a-TOCOPEEROL OB LIPOSOMAL LIPID PEROXIDATION. A. Pinson, G. Link, C. Herd&o. Lab. for Myocardial I&a., Hebrew University-Eiadassah Medical School and Dep. of Medicine, Shaare Zedek Medical Center, Jerusalem, Israel. MDA formation in iron-loaded heart cells in culture implies that lipid peroxidation occurs (Hershko & a&, J. Lab. Clin. Med., 110, 355, 1987). However, onlv minor changes in the fattv acid orofile (FAP) were observed in such cells. The effects of iron on ceilular lipid composition were studied using liposomes prepared from lipids extracts of cultured heart cells. FAP's were determined as functions of duration of incubation, pH, ascorbate, and a-tocopherol at 37'C. FAP was assessed by GC. The levels of all the unsaturated FA's (UFA's), mainly C203’. fell with decreasing -OH. At pH 5.5 and L.5 (about the PH prevailinp in lysosome Ln vivo), LTFA's were vi%ally idetectabl& $A concen&aiions were-markedly lower 2 these pHs after 3 h of incubation with iron, reaching a minimum after 12 h. Ascorbate at 0.01 mg/preparation enhanced the decrease in UFA, while a higher concentrations of ascorbate or a-tocopherol (1 mg/preparation) led to complete Since similar changes in FAP could not be inhibition of lipid peroxidation. demonstrated in intact cells, we propose that they either have a repair or a protective mechanism preventing lipid peroxidation, or that it is confined to the lysosomal cell compartment. Ongoing studies are directed towards further elucidation of this pathway. (This research is supported by NIH grant HL 34062-01 Al). S.56