Therefore, the aim of this study was to evaluate the effect of chronic kidney disease on changes in vasopressin system expression (mRNA and protein levels of V1a and V2 receptors and the protein level of aquaporin 2 (AQP2)) in the kidney cortex and in addition to assess the usefulness of plasma copeptin concentrations in the course of chronic kidney disease in rats with nephrectomy. This evidence concerns the gene AQP2 and chronic kidney disease.