Differential expression of aquaporins in the kidneys of streptozotocin-induced diabetic mice.
OBJECTIVE
Aquaporins (AQPs) are members of the water channel family and are important in renal physiology as it affects urinary concentration. The downregulation of aquaporins is often observed in polyuria associated with acquired nephrogenic diabetes insipidus. In this study, we examined the expression of AQP1, AQP2, AQP3 and AQP4 in streptozotocin (STZ)-induced diabetic mice.


RESULTS
By semiquantitative reverse transcription-polymerase chain reaction, we detected no change in the gene expression of AQP1 or AQP4 in whole kidney among STZ-induced diabetic mice (STZ mice) and sham (control group that received citrate buffer injection only). In contrast, we found less AQP2 or AQP3 mRNA expression in the whole kidney from STZ mice. Immunoblotting studies confirmed no difference in AQP1 or AQP4 protein expression of whole kidney between STZ mice and sham. However, there was less AQP2 or AQP3 protein expression in the whole kidney from STZ mice as compared to sham. By immunochemical staining, the reduction of AQP2 protein was localized to the principle cells of the collecting ducts. The expression of cortical AQP3 (especially the outer cortex, the S1 and S2 segments of the proximal tubules) was downregulated in STZ mice whereas the expression of AQP3 protein in medullary collecting ducts was similar to that of sham.


CONCLUSIONS
Our results reveal that the water transport in urinary concentration involves the downregulation of AQP2 and AQP3 expression in STZ mice.
Leung
Joseph Ck
JC
Division of Nephrology, Department of Medicine, Queen Mary Hospital, The University of Hong Kong, Pokfulam, Hong Kong.
Chan
Loretta Yy
LY
Tsang
Anita Wl
AW
Tang
Sydney Cw
SC
Lai
Kar Neng
KN
D000818:Animals; D000918:Antibody Specificity; D051398:Aquaporin 1; D051399:Aquaporin 2; D051400:Aquaporin 3; D051401:Aquaporin 4; D020346:Aquaporins / Q000235:genetics* / Q000276:immunology / Q000378:metabolism*; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D015870:Gene Expression / Q000502:physiology; D015151:Immunoblotting; D007668:Kidney / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL
C496021:Aqp1 protein, mouse; C496024:Aqp2 protein, mouse; C496028:Aqp3 protein, mouse; C496031:Aqp4 protein, mouse; D051399:Aquaporin 2; D051401:Aquaporin 4; D020346:Aquaporins; D051398:Aquaporin 1; D051400:Aquaporin 3