Cisplatin Decreases the Abundance of Aquaporin Water Channels in Rat Kidney

Abstract . The present study examined whether the cisplatininduced urinary concentration defect can be related to an altered regulation of aquaporin (AQP) water channels in the kidney. Cisplatin (8 mg/kg) was injected intraperitoneally into male Sprague-Dawley rats. The control group was without cisplatin treatment. Four d later, the expression of AQP1, AQP2, and AQP3 proteins was determined in the kidney. To specify further the primary point of derangement in the pathway that activates the arginine vasopressin—mediated AQP channels, different components of adenylyl cyclase complex were examined separately. The cisplatin treatment caused a polyuric renal failure in association with decreases of free water reabsorption. The expression of AQP1 and AQP2 was decreased in the cortex, the outer medulla, and the inner medulla, whereas that of AQP3 was decreased in the outer medulla and the inner medulla. The expression of AQP2 proteins in the apical membrane-enriched fraction decreased in parallel with that in the subapical vesicle-enriched fraction, indicating a preserved targeting. Immunohistochemistry of the outer medulla also revealed that cisplatin decreased immunoreactivity for AQP1, AQP2, and AQP3. The arginine vasopressin—evoked generation of cyclic adenosine monophosphate was attenuated by cisplatin, being most prominent in the outer medulla. However, the cyclic adenosine monophosphate generation in response to forskolin was not affected, whereas that to sodium fluoride was diminished significantly. Cisplatin also decreased the expression of Gsα proteins in the outer medulla and the inner medulla. These results suggest that a reduced expression of AQP water channels accounts at least in part for the cisplatin-induced urinary concentration defect.