Background and purpose <p>A noninvasive and accurate indicator for evaluating direct renal effects after remote ischemia preconditioning (RIPC) is currently lacking. To explore the feasibility of R<sub>2</sub>’ mapping in evaluating the direct effect of RIPC on rabbit kidneys and to investigate the mechanisms underlying renal changes induced by RIPC.</p> Methods <p>Eighteen healthy New Zealand rabbits were used (RIPC group, N = 12; control group, N = 6). RIPC was achieved with three cycles of bilateral hindlimb ischemia (10 min/cycle, 60 min total). Magnetic resonance imaging was performed at 1 and 24 hours after RIPC. The R<sub>2</sub>’ values of the renal cortex, outer medulla, and inner medulla were then recorded. Femoral arterial blood was collected for blood gas analysis and measurements of electrolytes. Enzyme-linked immunosorbent assay was used to detect the levels of myeloperoxidase (MPO), malondialdehyde (MDA), and superoxide dismutase (SOD). Immunohistochemical staining was used to detect the average optical density (AOD) of hypoxia-inducible factor 1 alpha (HIF1α). One-way analysis of variance or the Kruskal–Wallis test was used to assess differences among the groups. Correlations were evaluated using the Spearman rank correlation coefficient.</p> Results <p>The R<sub>2</sub>’ values of the renal cortex, outer medulla, and inner medulla in the RIPC groups were significantly lower than those in the control group (RIPC 1&#xa0;h group: each <i>P</i> &lt; .001; RIPC 24&#xa0;h group: <i>P</i> = .002, <i>P =</i> .002, <i>P</i> &lt; .001, respectively). MPO levels in the RIPC 1&#xa0;h and 24&#xa0;h groups were significantly lower than those in the control group (<i>P</i> = .02, <i>P</i> = .004, respectively). SOD levels in the RIPC 1&#xa0;h group were significantly higher than in the control group (<i>P</i> = .001). HIF1α AOD in the RIPC 1&#xa0;h and 24&#xa0;h groups were significantly higher than those in the control group (both <i>P</i> &lt; .001). The R<sub>2</sub>’ values of the renal cortex, outer medulla, and inner medulla positively correlated with myeloperoxidase level (<i>r</i><sub><i>s</i></sub>=0.78, <i>P</i> &lt; .001; <i>r</i><sub><i>s</i></sub>=0.78, <i>P</i> &lt; .001; <i>r</i><sub><i>s</i></sub>=0.78, <i>P &lt;</i> .001), and negatively correlated with superoxide dismutase level (<i>r</i><sub><i>s</i></sub>=-0.81, <i>P &lt;</i> .001; <i>r</i><sub><i>s</i></sub>=-0.74, <i>P</i> &lt; .001; <i>r</i><sub><i>s</i></sub>=-0.69, <i>P =</i> .002), and HIF1α AOD (<i>r</i><sub><i>s</i></sub>=-0.74, <i>P</i> &lt; .001; <i>r</i><sub><i>s</i></sub>=-0.55, <i>P</i> = .02; <i>r</i><sub><i>s</i></sub>=-0.71, <i>P &lt;</i> .001).</p> Conclusion <p>R<sub>2</sub>’ mapping can quantitatively assess kidney effects after remote ischemia preconditioning, and remote ischemia preconditioning can effectively enhance renal antioxidant capacity and oxygen uptake.</p>

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Evaluation of the direct effect of remote ischemic preconditioning on the rabbit’s kidney by R2’ mapping technique: an experimental study

  • Zhangyan Bi,
  • Zhaoyu Xing,
  • Longfei Huang,
  • Xintian Yu,
  • Jiule Ding,
  • Jie Chen,
  • Wei Xing,
  • Liang Pan

摘要

Background and purpose

A noninvasive and accurate indicator for evaluating direct renal effects after remote ischemia preconditioning (RIPC) is currently lacking. To explore the feasibility of R2’ mapping in evaluating the direct effect of RIPC on rabbit kidneys and to investigate the mechanisms underlying renal changes induced by RIPC.

Methods

Eighteen healthy New Zealand rabbits were used (RIPC group, N = 12; control group, N = 6). RIPC was achieved with three cycles of bilateral hindlimb ischemia (10 min/cycle, 60 min total). Magnetic resonance imaging was performed at 1 and 24 hours after RIPC. The R2’ values of the renal cortex, outer medulla, and inner medulla were then recorded. Femoral arterial blood was collected for blood gas analysis and measurements of electrolytes. Enzyme-linked immunosorbent assay was used to detect the levels of myeloperoxidase (MPO), malondialdehyde (MDA), and superoxide dismutase (SOD). Immunohistochemical staining was used to detect the average optical density (AOD) of hypoxia-inducible factor 1 alpha (HIF1α). One-way analysis of variance or the Kruskal–Wallis test was used to assess differences among the groups. Correlations were evaluated using the Spearman rank correlation coefficient.

Results

The R2’ values of the renal cortex, outer medulla, and inner medulla in the RIPC groups were significantly lower than those in the control group (RIPC 1 h group: each P < .001; RIPC 24 h group: P = .002, P = .002, P < .001, respectively). MPO levels in the RIPC 1 h and 24 h groups were significantly lower than those in the control group (P = .02, P = .004, respectively). SOD levels in the RIPC 1 h group were significantly higher than in the control group (P = .001). HIF1α AOD in the RIPC 1 h and 24 h groups were significantly higher than those in the control group (both P < .001). The R2’ values of the renal cortex, outer medulla, and inner medulla positively correlated with myeloperoxidase level (rs=0.78, P < .001; rs=0.78, P < .001; rs=0.78, P < .001), and negatively correlated with superoxide dismutase level (rs=-0.81, P < .001; rs=-0.74, P < .001; rs=-0.69, P = .002), and HIF1α AOD (rs=-0.74, P < .001; rs=-0.55, P = .02; rs=-0.71, P < .001).

Conclusion

R2’ mapping can quantitatively assess kidney effects after remote ischemia preconditioning, and remote ischemia preconditioning can effectively enhance renal antioxidant capacity and oxygen uptake.