# Metabolic and Microcirculatory Changes in Severe Renal Ischemia–Reperfusion and Ischemic Preconditioning in the Rat: Are They Detectable in the First Hour of Reperfusion?

## TL;DR

This study examines early metabolic and microcirculatory changes in rat kidneys after ischemia-reperfusion and ischemic preconditioning, focusing on the first hour of reperfusion.

## Contribution

The study provides new insights into the early detectability of microcirculatory and metabolic changes in renal ischemia-reperfusion and the limited protective effects of ischemic preconditioning.

## Key findings

- Both ischemic groups showed micro-rheological impairment and elevated potassium, lactate, and creatinine levels.
- Ischemic preconditioning resulted in less deterioration of blood flow and better microcirculation values.
- The protective effects of ischemic preconditioning were limited within the first hour of reperfusion.

## Abstract

Ischemia–reperfusion (I/R) strongly affects a graft’s function and survival and modulates microcirculatory and hemorheological parameters. However, the boundary between the reversibility and irreversibility of damage is unclear. This study compared the effects of renal I/R and ischemic preconditioning (IPC) to determine whether metabolic, microcirculatory, and micro-rheological changes are already detectable in the first hour of reperfusion. Wistar rats were divided into control (n = 6), I/R (n = 7) and IPC (n = 7) groups. In the ischemic groups the left kidney was subjected to 120 min of ischemia followed by 60 min of reperfusion. In the IPC group, a 3 × 5 min protocol was used prior to the manifest ischemia. Parenchymal microcirculation and renal artery blood flow were measured before ischemia (base) and during reperfusion (R-30, R-60). Hematological, micro-rheological parameters, electrolytes, and metabolites were tested at base and at R-60. Both ischemic groups showed micro-rheological impairment. An increase in potassium, lactate, and creatinine concentrations and a decrease in pH were observed. The blood flow of the IPC group deteriorated less, and microcirculation recordings indicated better values. The 120 min ischemia and the 60 min reperfusion resulted in micro-rheological and metabolic alterations, together with decreased renal blood flow and parenchymal microcirculation. Although the applied IPC protocol showed minor protective effects, its impact was limited in the first hour of reperfusion.