Diabetes constitutes a group of metabolic diseases characterized by hyperglucemia as a result of defective insulin secretion, insulin action or a combination of both factors. Its classic symptoms polydipsia, polyuria, polyphagia and loss of body weight. Until now, the genesis of polyuria has been considered an osmotic effect, resulting from glucose remaining in the tubule. Glucose filters freely through the glomerular filtration barrier and is later reabsorbed in the proximal tubule by two transporters: SGLT1 and SGLT2. During diabetes there is an increase in the filtered glucose load, transporters get saturated, and glucose remains in the tubular fluid, exerting an osmotic effect which prevents glucose reabsorption. Aquaporin 1 (AQP1) is a water channel strongly expressed in the proximal tubule, where 70% of filtered water is reabsorbed. It has a hypertonicity response element. Although
AQP1 protein mediates water reabsorption, and polyuria is a hallmark of diabetes, its role in the genesis of said polyuria has never been studied. Here, our aim was to study the expression and localization of AQP1, and its possible role in the genesis of polyuria. Diabetes was induced on mal Sprague Dawley rats (180-200 g) by injection of Streptozotocin (STZ, 65 mg/kg). Studies were performed 15 days and 5 months after diabetes development. Results: Western blot (WB) performed on kidney cortex obtained from diabetic rats 15 days after diabetes induction showed a significant increase in AQP1 expression. Immunofluorescence studies were performed to determine protein localization. These studied showed an increase in AQP1 signal in the apical membrane of proximal tubular cells. 5 months after diabetes development, WB studies showed a significant decrease in AQP1 expression. Immunofluorescence confirmed this result. Our results suggest polyuria, a hallmark symptom of diabetes could not only be related to an osmotic effect due to glucose remaining in the tubular fluid, but could also be attributed to changes in AQP1 expression. More studies are needed to clarify the role and regulation of AQP1 in the diabetic kidney in order to implement new therapeutic strategies.