Tehran University Medical Journal

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Background: Several studies indicate that gender differences exist in tolerance of the kidney to ischemia reperfusion (IR) injury. Recently, postconditioning (POC), induction of brief repetitive periods of IR, has been introduced to reduce the extent of the damage to the kidney. This method was shown to attenuate renal IR injury by modifying oxidative stress and reducing lipid peroxidation. Considering the gender effect on the results of several treatment methods, in this study, we investigated the impact of gender on the protective effect of POC on the rat kidney.
Methods: In this study, after right nephrectomy, 48 male and female rats were randomly divided into 6 groups of 8 rats: In IR group, with the use of bulldog clamp, 45 minutes of left renal artery ischemia was induced followed by 24 hours of reperfusion. In the sham group, all of the above surgical procedures were applied except that IR was not induced. In the POC group, after the induction of 45 minutes ischemia, 4 cycles of 10 seconds of intermittent ischemia and reperfusion were applied before restoring of blood to the kidney. 24 hours later, serum and renal tissue samples were collected for renal functional monitoring and oxidative stress evaluation.
Results: Postconditioning attenuated renal dysfunction considering the significant decrease in plasma creatinine and BUN compared with IR group only in male rats (P<0.05). Also, POC attenuated oxidative stress in male rats’ kidney tissues as demonstrated by a significantly reduced malondialdehyde (MDA) level and increased superoxide dismutase (SOD) activity (P<0.05). In female rats, there were no changes in functional markers and oxidative stress status in POC group compared to IR group.
Conclusion: Considering gender difference, POC had protective effect against IR injury by attenuating functional and oxidative stress markers in male rat kidneys. This protective effect was not seen in female rats.

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Background: The renal sympathetic nerve activity (RSNA) is enhanced in renal failure. Paraventricular nucleus in hypothalamus is an important central site to regulate sympathetic activity. There are angiotensin II (Ang) II receptors in this nucleus. The aim of this study was to evaluate the effects of angiotensin II in hypothalamic paraventricular nucleus (PVN) on renal ischemia-reperfusion injury and RSNA. Methods: This study was done at 2013 in Physiology department of Tehran University of Medical Sciences. One week before the induction of renal Ischemia-Reperfusion (IR) in Sprague-Dawley rats, a cannula was inserted into the right PVN for microinjection of different doses of Ang II (3, 30, and 300 ng). Then right nephrectomy was done. After one week recovery, renal IR injury was induced by clamping the left renal artery for 45 minute and then reperfusion for 3 or 24 hour. Ten minutes before the induction of renal ischemia-reperfusion, administration of different doses of angiotensin II were done in different groups. In all animals, left renal sympathetic activity was recorded before and during renal ischemia. After 3 or 24 hours reperfusion the blood, kidney and brain were collected to assay renal function and histology and oxidative stress indices Superoxide Dismutase, SOD and Malondialdehyde, MDA) in PVN. Results: Administration of different pharmacological doses of angiotensin II into PVN exaggerated the renal IR injury. Angiotensin II in different doses increased the plasma creatinine and BUN levels and renal histological markers in comparison to renal IR in-jury (P<0.05). Angiotensin II had detrimental effects on RSNA and oxidative stress in-dices Super Oxide Dismutase (SOD) and Malondialdehyde (MDA) in PVN as the dose was increased (P<0.05). Conclusion: These data showed that the PVN is a responsive site for central Ang II-induced damage in renal IR injury. We suggested the central effects of Ang II in the PVN on renal IR injury are mediated by oxidative stress in the PVN, and the peripheral effects by a sympathetic pathway.