2003; Yamasowa 2004). The CD represents the final site of regulated water reabsorption from the tubular fluid and is usually thought to be relatively resistant to ischemic insult (Kortenoeven and Fenton 2014). Nevertheless, it has been demonstrated that I/R injury downregulates CD AQPs (Fernández‐Llama et al. 1999; Gong et al. 2004; Kwon et al. 1999) and that pharmacological intervention using erythropoietin prevents the ischemia‐induced downregulation of AQP2 and improves urinary concentration capability (Gong et al. 2004). The gene discussed is AQP2; the disease is ischemia.