The Experimental Research Of Renal Aquaporin-2 Expression In Obstructive Jaundice

IntroductionThe obstructive jaundice ( OJ) can result in renal dysfunction, the first clinic manifestation is oliguria. One of the main complications of the operation of OJ is acute renal failure (ARF) whose character is necrosis of renal tubule. There is no advance in the investigation of how OJ leads to the physiological and pathological change in the kidney. The AQP - 2 locates at adelomorphous cell near proximal tubule and internal medullary mass of the collecting duct cellula epithelialis top cytolemma of the kidney. AQP - 2 participates in mediating the permeability of renal collecting duct which depends on the antidiuretic hormone (ADH). And it plays an important role in the mechanism of urine concentration. When OJ occurs, the blood capacity reduce, the ADH increase subsequently , AVP is activated. The expressions of AQP - 2 and AQP - 2 mRNA are controlled by ADH and AVP through long time and short time regulation. According to reports, the expressions of AQP - 2 and activated AQP - 2 decrease obviously in renal failure caused by ischemic reperfusion injury. In this study, we establish obstructive jaundice model with Wistar rats. The mechanism of renal dysfunction caused by obstructive jaundice is discussed through measuring the contents of serum Bilirubin, urea nitrogen and creatinine, and detecting the amount of AQP -2 and AQP -2 mRNA in kidney.Materials and MethodsFourty adult male Wistar rats, weight between 200 -250g, were selected in the experiment. All the rats were randomly divided into four (A, B, C, and D)group (n = 10). Group A is the rats that suffered obstructive jaundice for 7 days. Group B is the rats that suffered sham operation for 7 days. Group C is the rats that suffered obstructive jaundice for 14 days. Group D is the rats that suffered sham operation for 14 days. All the experimental rats were killed respectively in 7' day or 14' day after the experimental animal model of obstructive jaundice was established. Examine the liver function and renal function of each experimental animal. Then identify whether the animal model meet the experimental request. Western blotting method was used to detect the amount of AQP -2 in kidney. And RT - PCR technique was used to detect the expression of AQP-2mRNA in kidney.SPSS11.0 software was used for statistic analysis.Experiment result1. There is no significance in CREA examination between each experimental group (P >0. 05) . The level of UREA has extraordinary significance between group A and C and between group C and D (P < 0. 01) , whereas it has no significance between the others groups ( P >0. 05 ).2. The amount difference of AQP -2 between group A and C and between group C and D has extraordinary significance by using the Western blotting technique ( P <0. 01). The difference between group A and B has significance ( P< 0.05) , but between group B and D has no significance (P > 0. 05).3. The expression of AQP -2mRNA has extraordinary significance between group A and B and between group C and D and between group A and C by using the PCR technique ( P <0. 01). The expression difference between group B and D had no significance ( P >0.05).DiscussionThere are several main theories of ARF mechanism in obstructive jaundice in the surgical operation period, such as endotoxe mia , when the mucosal barrier of intestines is harmed;the harm of kidney in lacking of blood and infusingagain;the harm of kidney corned from bilirobin . Formerly,the examination of kidney function is limited in discussing the cause of the harm of kidney. In foreign countries there have been a great deal of reports that the renal AQP changed obviously when the kidney was harmed of medcine and lacking of blood. This discovery led us to research the pathogeny and changes of patho - physiology of the harm of kidney of obstructive jaundice in the surgical operation period. The AQP - 2 locates in aero - cytolemma of main cell of kidney proximal tubule and collecting duct epithelial cell in internal medullary mass . It has important function in the concentrated mechanism of urine.It is discovered in this test that obstructive jaundice can make the expression of renal AQP - 2 down obviously. This research confirmed that when obstructive jaundice the structure harm and function harm of different degree really appeared in kidney. The main reasons maybe the harm of epithelial cell in collecting duct of kidney caused by lacking of blood and cell factors such as nitrogen monoxidum and free radicle, added of the directly hame of collecting duct caused by bilirobin , endotoxe mia,all of above cause the protein express breakdown . Otherwise, because of the short time accommodation of the ADH, AVP, the live AQP - 2 increased on the tube membrane, part of AQP - 2 shed off in the tube and was rushed out by the urine. This possibility therefore make the AQP - 2 in kidney reduce obviously. In this experiment the expression ofrenal AQP -2mRNA increased. It may be caused by the long time accommodation of the ADH, AVP. Otherwise , in early time of renal dysfunction, collecting duct maybe still have the abillity of accommodating the expression of AQP -2. Yet, the expressive reinforce of renal AQP - 2 maybe the reflect of the ability of protein composition in endocytoplasmic reticulum .The rats and the persons AQPcDNA has been cloned all already , the gene constitutes to have commonness. So the changes of renal AQP -2 of rat that we reserched in obstructive jaundice can at certain degree up reflect the changes of renal AQP - 2 of person in obstructive jaundice.Conclusion1. The UREA of rat increased at 14l day in OJ, it means OJ can result in renal dysfunction.2. The expression of AQP -2 decrease in early stage of obstructive jaundice , and it decrease slowly along with the duration of obstructive jaundice.3. The expression of AQP -2 mRNA increase in obstructive jaundice, and it increase slowly along with the duration of obstructive jaundice.