Background: Intradialytic hypotension (IDH) is a critical pathological condition associated with all−cause mortality in patients undergoing hemodialysis (HD). However, few studies have investigated IDH-related changes in hepatic and cerebral regional tissue oxygen saturation (rSO2). This study investigated IDH-induced changes in hepatic and cerebral rSO2. Methods: Hepatic and cerebral rSO2 during HD were measured using an INVOS 5100C oxygen saturation monitor, and their percentage (%) changes during IDH development were analyzed. Ninety-one patients undergoing HD were investigated, including 20 with IDH development. Results: In patients with IDH, % changes in hepatic and cerebral rSO2 decreased at IDH onset. Additionally, the % change in hepatic rSO2 was significantly larger than those in cerebral rSO2 (P < 0.001). In patients without IDH, no significant differences were found between the % changes in hepatic and cerebral rSO2 at time of the lowest systolic blood pressure during HD. Multivariable linear regression analysis showed that the difference between the % change in cerebral and hepatic rSO2 was significantly associated with IDH development (P < 0.001) and ultrafiltration rate (P = 0.010). Conclusion: Hepatic and cerebral rSO2 significantly decreased in IDH development and hepatic rSO2 was more largely decreased than cerebral rSO2 at IDH onset.

Aquaporin-11 (AQP11) is an intracellular water channel expressed at the endoplasmic reticulum (ER) of the kidney proximal tubule. Its gene disruption in mice leads to intracellular vacuole formation at one week old and the subsequent development of polycystic kidneys at three week old. As the damaged proximal tubular cells with intracellular vacuoles later form cysts, autophagy may play a role in their survival. We examined the autophagy activity before and after the development of cysts in AQP11(-/-) kidneys. We first observed an enhanced expression of LC3 gene (Map1lc3b) as well as other autophagy-related genes in AQP11(-/-) mice by quantitative PCR analysis. We then examined the formation of autophagosomes visualized by a green fluorescent fusion protein, GFP–LC3 in its transgenic mice. The expression of GFP-LC3 puncta was increased in the proximal tubule of AQP11(-/-) mice before the cyst formation. Interestingly, they were also observed in the cyst-lining epithelial cell. Further PCR analyses revealed the enhanced expression of apoptosis- and ER stress-related caspase genes before and after the cyst formation suggesting that ER stress may have enhanced autophagy. We conclude that autophagy will play an important role in the development and the survival of the kidney cysts in AQP11(-/-) mice.