Abstract: 311

-TOCOPHEROL INHIBITS ACTIVATION OF THE ISOFORM OF PROTEIN KINASE C AND NADPH OXIDASE-MEDIATED GENERATION OF SUPEROXIDE ANION RADICALS IN LINDANE-EXPOSED MYOMETRIUM.

Chwen-Ting Wang^{1 *}, Rita Loch-Caruso^{1 *}
Toxicology Program, The University of Michigan, Ann Arbor, MI ¹

The insecticide lindane abolishes spontaneous uterine oscillatory contraction and induces superoxide generation. The present study investigated the role of calcium-independent protein kinase C (PKC) in lindane-induced inhibition of uterine contraction, and tested the hypothesis that -tocopherol inhibits superoxide production by inhibiting PKC-dependent activation of NADPH oxidase. In uterine strips excised from midgestation rats, lindane (30 M) induced a redistribution of PKC activity from the cytosol to the membrane, indicating activation of PKC. Omitting calcium only moderately diminished PKC activity, suggesting a calcium-independent activation of PKC by lindane. Standard muscle baths were used to measure isometric contractions. Inhibition of PKC with a specific inhibitor peptide significantly blocked the inhibitory effect of lindane (30 M) on uterine contraction. Moreover, lindane-stimulated PKC translocation from the cytosol to the membrane was inhibited by pretreatment with 200 M -tocopherol. Using dipheneylene iodonium as a specific NADPH oxidase inhibitor, NADPH-supplemented cytochrome c reduction was assayed in myometrial cell cultures with or without superoxide dismutase to measure superoxide generated specifically by NADPH oxidase. Lindane (100 M) exposure increased superoxide generation in a time (5-60 min) and concentration (30-100 M) dependent manner. Pretreatment with -tocopherol prior to lindane exposure decreased the amount of superoxide generated. These data suggest that 1) the activation of PKC is involved in lindane-induced inhibition of uterine contraction; 2) the lindane-induced production of superoxide anion radicals is mediated by the activation of NADPH oxidase by PKC; and 3) -tocopherol interrupts this activation pathway by inhibiting PKC translocation.

    This abstract is being presented on Monday, August 2 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.