[Expression of aquaporin in rats' endolymphatic sac and kidney and the effect of anti-diuretic hormone on the expression of aquaporin].

OBJECTIVE

To confirm the expression of aquaporin2,3,4 (AQP2,3,4, water channel protein) in rats' endolymphatic sac (ES) and kidney, and to investigate and compare the effects of antidiuretic hormone (AVP) and DDAVP [(deamino-Cys1,D-Arg8)-Vasopressin, V2-receptor agonist] on the expression of AQP2 in rats' ES and kidney.

METHODS

Thirty healthy Swards white rats were divided into the negative control, AVP group and dDAVP group, respectively, and were cardiaca perfused. The temporal bones and kidneys were taken out, then processed and sectioned by paraffin-embedded technique. The sections of ES were labeled with fluorescent antibody by immunohistochemical method, and kidney's with avidin-biotin-peroxidase complex method (ABC). The expression of AQP-2,3,4 were confirmed in the ES of rats, and the different effects of the AVP and DDAVP onto the ES and kidney were observed. The slides used were analyzed by image-analyzer and the subsequent data were dealt with statistically.

RESULTS

In the cytomembrane and cytoplasm of ES' epithelia, the constant and clear fluorescent reaction could be observed in normal control group with the first antibody of AQP2,3,4. Significant feeble fluorescent reaction of the first antibody of AQP-2 was revealed in AVP group and DDAVP group and showed much lower of gray (P < 0.01), less intensive of fluorescent (P < 0.01) under the fluorescence microscope. In the principal cell of renal collecting duct, it was on the contrary. Compared with the control group, significant stain was revealed in AVP group and DDAVP group and showed lower of gray (P < 0.05), greater density (P < 0.05), higher IOD (P < 0.05) and more stained area (P < 0.05). There is no different between the AVP group and DDAVP group in expression of AQP-2 in two sites.

CONCLUSIONS

AQP-2,3,4 were expressed both in rats' epithelia of endolymphatic sac (ES) and principal cell of renal collecting duct. AVP promotes the expression of AQP2 in kidney but inhibits in ES. AVP maybe play important role to control the expression of AQP-2 in ES and kidney probably by the role of AVP-V2R-cAMP-AQP2.