Impact of Light-Dark Cycle Patterns on Oxidative Stress in an Adriamycin-Induced Nephropathy Model in RatsReport as inadecuate

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The principal goal of this study was to determine the effect of the photoperiod on oxidative damage biomarkers in rats submitted to different light-darkness patterns, in a hyperlipidemic nephropathy model induced by adriamycin, as well as its possible relationship with melatonin and leptin secretion rhythms. To test this hypothesis, six different groups were used N = 6 rats per group: control 12 h-12h light:dark; exposure to permanent illumination 24 h light; exposure to darkness 22 h dark; injected with adriamycin, 12h-12h light:dark; injected with adriamycin + exposure to permanent illumination and injected with adriamycin + exposure to darkness 22 h dark. The different photoperiods were begun two weeks prior to medication and were maintained up to the day of the animal-s sacrifice, ten days after medication. The following parameters were analysed: i weight evolution; ii in plasma: urea, creatinine, uric acid, total proteins, albumen, lactate dehydrogenase, creatinine-quinase, aspartate aminotransferase, alanine aminotransferase and total cholesterol; iii in urine: urea, creatinine, total proteins and microalbumen; iv biomarkers of oxidative damage in kidneys, heart, liver and brain: lipoperoxides, total glutathione, reduced glutathione, catalase, glutathione peroxidase, glutathione reductase and glutathione transferase; v melatonin pineal gland tissue and plasma and leptin plasma. From the results obtained it was concluded that the administration of adriamycin generated oxidative stress in renal, cerebral, hepatic and cardiac tissue. Additionally, in the healthy animal, but of a lesser relevance in the adriamycin animal, permanent light worsened the oxidative stress, whereas darkness improved it. This could be related to the circadian rhythm of the inverse release shown by melatonin and leptin, accentuating the release of melatonin in the darkness phase and that of leptin in the light phase. The correlation between melatonin and leptin in the healthy animal seemed to confirm the relationship between both variables and their influence on oxidative damage biomarkers.

Author: Begoña M. Escribano , Antonia Moreno , Inmaculada Tasset, Isaac Túnez



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