Abstract Background and Aims Renal ischemia–reperfusion (RIR) injury is one of the factors in the development of acute kidney injury (AKI). AKI is multifactorially caused, but the mechanism of pathogenesis and development of this disease is still incompletely defined. AKI is characterized by the sudden appearance, rapid progression of disease and very uncertain and often fatal outcome. Heme oxygenase-1 (HO-1) is a cytoprotective enzyme that catalyzes the breakdown of heme to biliverdin, carbon monoxide, and iron. HO-1 is now recognized as a protection factor in acute kidney injury. The aim of this study was to determine the effect of preconditioning with hyperbaric oxygen (HBO) on HO-1 expression in kidney tissue and kidney function in spontaneously hypertensive rats (SHR) during kidney ischemia–reperfusion injury. Method An experiment was performed in anesthetized, adult six-month-old male SHR. The right kidney was removed and the renal ischemia was performed by clamping the left renal artery for 40 minutes. SHR were randomly selected in three experimental groups: sham operated group (SHAM; n=7); AKI control group (AKI; n=9); and AKI group with HBO (AKI+HBO; n=9). Treated group were placed into experimental HBO chambers and exposed to pure oxygen, twice a day (in a 12 hour period, 8AM and 8 PM) for two consecutive days in the following manner: 10 minutes slow compression, 2.026 bar for 60 minutes, 10 minutes slow decompression. Mean arterial pressure (MAP) and HO-1 expression in kidney tissue were measured 24h after reperfusion. Clearance of creatinine (CCr), urea (CUr) and phosphate (CPh) were calculated 24h after reperfusion. Results After AKI induction reduction of blood pressure was recorded in both groups with AKI. Preconditioning with HBO significantly improved kidney function in rats with AKI compared to control group. HO-1 expression in kidney tissue was significantly higher in the treated group (p<0,01) compared to SHAM and AKI control group. Conclusion Our results suggest that HBO treatment improves kidney function in the AKI+HBO vs. AKI control group. This implies that increased level of HO-1 due to preconditioning with hyperbaric oxygen may have beneficial effects on kidney function, and potentially protective effect in an ischemic model of AKI with hypertension.