[Effects of erythropoietin on the expression of aquaporin-2 after renal ischemia-reperfusion injury: experiment with rats].
OBJECTIVE
To investigate the effects of erythropoietin (EPO) on the expression of aquaporin 2 (AQP(2)) after renal ischemia/reperfusion (IR).


METHODS
Twenty-four Wistar rats were randomly divided into 3 equal groups: IR group undergoing resection of the right kidney, closuring of the left renal artery, vein, and ureter, and un-closuring 40 min later; IR + EPO group undergoing the above mentioned procedures and then intraperitoneal injection of EPO 3000 U/kg on days 1 and 2 after the treatment; and control group undergoing resection of the right kidney only without IR of the left kidney. Urine volume and urine osmotic pressure were measured. Blood samples were collected to detect the serum blood urea nitrogen (BUN) and creatinine (Cr). Three days after the treatment the kidneys were taken out. RT-PCR and Western blotting were used to detect the mRNA and protein expression of AQP(2).


RESULTS
The urine volume of the IR + EPO group was (26.0 +/- 2.3) microl .min(-1).kg(-1), significantly lower than that of the IR group [(59.1 +/- 1.3) microl .min(-1) . kg(-1), P < 0.01]. The urine osmotic pressure of the IR + EPO group was (1508 +/- 121) mOsm/kg H(2)O, significantly higher than that of the IR group [(235 +/- 99) mOsm/kg H(2)O, P < 0.01]. The serum BUN and Cr levels of the IR + EPO group were (12.3 +/- 6.0) mmol/L and (51 +/- 5) micromol/L respectively, both significantly lower than those of the IR group [(29.9 +/- 3.7) mmol/L and (141 +/- 5) micromol/L respectively, both P < 0.01]. The mRNA and protein expression of AQP(2) were highly positive in the control group. The protein expression levels of AQP(2) of the IR + EPO group were not significantly different from those of the control group (both P > 0.05), and the protein expression levels of AQP(2) of the IR group were significantly lower than those of the control group (both P < 0.01).


CONCLUSIONS
EPO can inhibit the down-regulation of AQP(2) in response to IR and this may take part in the EPO protective mechanism of renal ischemia/reperfusion injury.
Wang
Hai-bo
HB
Transplantation Center, Second Affiliated Hospital of Dalian Medical University, Dalian 116027, China. whbsw2005@126.com
Wang
Li-ming
LM
Zhang
Ri-xin
RX
Liang
Rui
R
D000818:Animals; D051399:Aquaporin 2 / Q000096:biosynthesis*; D004195:Disease Models, Animal; D004921:Erythropoietin / Q000494:pharmacology*; D005260:Female; D007668:Kidney / Q000098:blood supply* / Q000187:drug effects / Q000378:metabolism; D007674:Kidney Diseases / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D015427:Reperfusion Injury / Q000378:metabolism*
D051399:Aquaporin 2; D004921:Erythropoietin