Background:
Chronic kidney disease (CKD) is an ongoing global problem. It is correlated with a substantial increase in mortality and morbidity. Although, hydrogen sulfide (H₂S) plays an important role in the physiological and pathological processes in the kidney, the influence of CKD on the enzymatic synthesis and utilization of H₂S in the kidney is unclear. The aim of this study was to evaluate the activity of H₂S-producing enzymes (сystathionine gamma-lyase, cystathionine beta-synthase and cysteine aminotransferase) and the content of H₂S in rats with CKD, and to establish the relationship between these parameters and markers of the functional state of the kidneys.

Material and methods:
CKD in rats was induced by 5/6 nephrectomy of the contralateral kidney. H₂S regulation was examined in post-nuclear kidney homogenates by measuring H₂S levels and cystathionine gamma-lyase, cystathionine beta-synthase, and cysteine aminotransferase activity using spectrophotometric methods. Functional and biochemical measurements were monitored after water load (5% of body mass).

Results:
CKD in rats was associated with defects in H₂S metabolism in rat kidneys. The activity of H₂S-producing enzymes decreased by 28.3-34.2% (p<0.05), the rate of utilization of exogenous H₂S in the kidneys increased by 34.3% (p<0.05), and the content of H₂S was reduced by 35.8% (p<0.05) in comparison with a control group. A progressive loss of kidney function (tubular and glomerular disorders) is closely correlated with the content of H₂S in the kidneys.

Conclusions:
The H₂S system in kidneys may be an important metabolic target, which can influence the efficacy of treatments to improve the functional state of kidneys in CKD.