Browsing by Author "Theron, C. N."

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    Inhibitory effects of non-steroidal anti-inflammatory drugs on human myeloperoxidase
    (Health & Medical Publishing Group, 1979) Theron, C. N.; Lubbe, S.; Van Zyl, A.
    Myeloperoxidase with an A420!280 ratio of 0,48 was prepared from normal human leucocytes. This partially purified preparation catalysed guaiacol oxidation, iodination of bovine serum albumin and de-iodination of 1251-thyroxine. Non-steroidal anti-inflammatory drugs (naproxen, indomethacin and f1ufenamic acid) showed a significant inhibitory effect on myeloperoxidase-catalysed iodination at concentrations of 10"4M and higher. Guaiacol also inhibited myeloperoxidase-catalysed iodination, and its iodination inhibition curve was nearly identical to that obtained with the anti-inflammatory drugs. At concentrations between 10"'M and 10"M the antiinflammatory drugs had very little or no effect on thyroxine de-iodination. Flufenamic acid and indomethacin, however, inhibited de-iodination significantly at a concentration of 10'M. It is postulated that non-steroidal anti-inflammatory drugs may inhibit myeloperoxidase-catalysed protein iodination by acting as oxidizable cofactors which compete with other oxidiza'ble substrates for oxidants formed by the peroxidase-hydrogen peroxide complex. In view of this and because the myeloperoxidase-hydrogen peroxide system may be involved in inflammatory tissue damage, the possibility should be considered that the action of non-steroidal anti-inflammatory drugs is at least partly attributable to a radical scavenging effect or to sequestration of oxidants.
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    Sex-dependent differences in phenobarbitone-induced oestradiol-2-hydroxylase activity in rat liver
    (Health & Medical Publishing Group, 1981) Theron, C. N.; Neethling, A. C.; Taljaard, J. J. F.
    Oestradiol-2-hydroxylase (E2-OH) activity was measured in liver and brain microsomes of 6-8-week-old Wistar rats. Phenobarbitone (75 mg/kg daily for 3 days) significantly increased enzyme activity in the liver of males and females, but there were striking differences between the two sexes. In males the enzyme activity was increased by 37% over control values and in females by 200%. The total microsomal cytochrome P-450 content was increased by 75% in males and by 82% in females. The apparent Michaelis constant (Km) of E2-OH for 17β-oestradiol in untreated males (9.8 μM) and females (9.2 μM) did not differ significantly. Phenobarbitone treatment, however, tended to reduce the apparent Km in males (8.2 μM) and to increase it in females (18.7 μM). E2-OH activity was also detected in brain tissue of both sexes, but it was 50-200-fold lower than in the liver and was not increased by phenobarbitone.