Expression of aquaporins, vasopressin type 2 receptor, and Na+₋K+₋Cl⁻ cotransporters in the rat endolymphatic sac.

Conclusion: Since many water channels and pumps, such as aquaporin (AQP) 1-4, AQP6-9, vasopressin type 2 receptor (V(2)-R), Na(+)-K(+)-Cl(-) cotransporter (NKCC) 1, and NKCC2 were expressed in the rat endolymphatic sac, it should play an important role in the physiological function of acid-based metabolism and water balance in endolymphatic fluid homeostasis.
Objective: To evaluate the expression and immunolocalization of AQP1-9, V(2)-R, NKCC1, and NKCC2 in the rat endolymphatic sac.
Materials and Methods: Wistar rats were used. Expression of AQP1-9, V(2)-R, NKCC1, and NKCC2 mRNA in the rat endolymphatic sac was investigated using the reverse transcription-polymerase chain reaction (RT-PCR) method, and detailed immunolocalization of AQP1-9, V(2)-R, NKCC1, and NKCC2 was investigated using immunohistochemical methods, including immunofluorescence microscopy.
Results: mRNAs and proteins of AQP1-4, AQP6-9, V(2)-R, NKCC1, and NKCC2 were expressed, but AQP5 was not expressed in the rat endolymphatic sac.