Research On Expression Of AQP1 In The Kidney Of Wistar Rat During Development

Objective:As recognized, the kidney is the champion organ with regard to fluid transport, AQP1 plays a vital role in the adjustment process of homeostasis in the organism, and the adjustment of electrolyte metabolism is a key. Water transmembrane transport is one of the most essential factors during the process. Water is transported mainly the membrane by aquaporins (AQPs). At present, at least 13 members (AQP0-AQP12) have been found in mammals, which are localized in cells of different tissues and organs. Up to now, less than eight types of AQPs have been found in the kidney, such as AQP1, AQP2, AQP3, AQP4, AQP6, AQP7, AQP8 and AQP11. Among them, AQP1 is widely expressed in membrane of the apical and basolateral membrane of the proximal tubule, the descending thin limb of medullary loop and the endothelium of the descending vasa recta. It is an important structure for water resolving. So its expression study is important for the investigating in the chang of the urinary concentrating mechanism.There is difference in the urinary concentrating function of the kidney during different development period of the human and animal, and there are also largely differences in the AQPs expressed. Although genetic expression of AQP1 have been studied from newborn to adult animal by some scientists. However, nothing is known about the expression of AQP1 from the newborn to the aged. Therefore, the purpose of the paper's study was to observe and analyze the expressive rule of AQP1 during kidney development different period of Wistar rat. It will provide our understanding on the physiological function of AQP1 in kidney during developmental different period, and provides the theoretical data of morphology for further investigating the expressive rule of AQP1 and other aquaporins.Materials and Methods:Male Wistar rats from Jilin University were used in the experiments. Kidneys were obtained from postnatal 1-, 7-, 14-, 21-, 28-day-old pups, and 3-, 6-, 9-, 12-, 15-, and 18-month-old adult rats. They were fixationed by 10% neutral formalin.The routine paraffin section were detected by means of hematoxylin and eosin-stained, immunohistochemical staining, light microscope technique for observing localization of AQP1, as well as computerized densitometry of image analytical system to measure quantitatively the expression of AQP1 in these sections.Results:1. Result of hematoxylin and eosin-stainedAt 1d of age: Cortex and medulla of rat kidney had been formed, and was during development. In the renal cortex, the volume of renal corpuscle and the lumens of renal tubule were smaller. In the renal medulla, renal tubule could be devided into the proximal straight tubules, the distal straight tubules and thin segment. And there were many vasa recta around the renal tubules.At 7d of age: Cortex and medulla of the kidney was during development. The structure of the renal tubule was similar to that at 1d of age after birth.At 14d of age: The volume of renal corpuscle and the lumens of renal tubule were obviously increased, and the lumens of renal tubule are clear.At 21d of age: The volume of renal corpuscle and the lumens of renal tubule still were increasing. The structure the renal tubules was similar to that at 14d of age after birth. At 28d of age: The volume of renal corpuscle and the lumens of renal tubule still were increasing.At 3m of age: The volume of renal corpuscle and the lumens of renal tubule still were increasing. The lumens of renal tubule in the superficial cortex were stained in acidophilia, and the lumen of renal tubule stained was decrease in the juxtamedullary cortex. It was not acidophilia in the renal medulla.At 6m of age: The volume of renal corpuscle and the lumens of renal tubule still increasing. Cylindric things were observed in the renal tubule of the superficial cortex. There were cylindric things in the tubule of the renal medulla.At 9m of age: The volume of renal corpuscle and the lumens of renal tubule were not evident change compared with at 6m of age after birth. Cylindric things observed were increasing in the renal tubule of the superficial cortex and the juxtamedullary cortex.At 12m of age: The volume of renal corpuscle and the lumens of renal tubule were not evident change compared with that at 9m of age after birth. Staining was weakly in the renal tubule of the superficial cortex. In the renal tubule of cortex, acidophilia things were more than that at 9m of age after birth.At 15m of age: Staining was light in the renal tubule of the superficial cortex. Cylindric things were increasing in the renal tubule of the cortex. At the same time, small quantities of cylindric things were observed in the tubule of the renal medulla.At 18m of age: The volume of renal corpuscle and the lumens of renal tubule was not evident change compared with at 9m of age after birth. Staining was weakly in the renal tubule of the superficial cortex. At the same time, there were some acidophilia things in the tubule of the renal medulla.2. Results of immunohistochemical stainingBackground of all of paraffin section stained is clear, positive reaction of AQP1 was brown. AQP1 primarily existed in cellular membrane and / or cytoplasm. Negative control had not been stained.At 1d of age: In the superficial cortex, the expression of AQP1 was weakly in the proximal convoluted tubule. In the juncture of renal cortex and medulla, the expression of AQP1 was stronger than that in the superficial cortex. In the medulla, the expression of AQP1 was strong in the descending thin limb medullary loop of and in the endothelium of the descending vasa recta surroundinging the medullary loop; however, it was faint in the tubule of renal medulla.At 7d of age: In the renal tubule of cortex, the expression of AQP1 was very weakly. It was obviously weaken compared with at 1d of age. In the juncture of renal cortex and medulla, the expression of AQP1 was stronger than in the renal tubule of superficial cortex. In the medulla, the expression of AQP1 was stronger in the descending thin segment medullary loop of and in the endothelium of the descending vasa recta.At 14d of age: In the superficial cortex, the expression of AQP1 was weakly in the proximal convoluted tubule. It is not obviously difference compared with at 7d of age. In the juncture of renal cortex and medulla, the expression of AQP1 was stronger than in the renal tubule of superficial cortex. The AQP1 was expressed in the descending thin segment medullary loop and the endothelium of the descending vasa recta.At 21d of age: In the superficial cortex, the expression of AQP1 was weakly in the proximal convoluted tubule. In the juncture of renal cortex and medulla, it was not obviously difference compared with at 14d of age. The AQP1 expression was strongly in the descending thin segment medullary loop.At 28d of age: In the superficial cortex, the juncture of renal cortex and medulla, as well as the medulla, it was not almost obviously difference compared with at 21d of age. At 3m of age: In the superficial cortex, the staining intensity in the proximal convoluted tubule. In the juncture of renal cortex and medulla, the expression of AQP1 was weak. The expression of AQP1 was more in the descending thin segment medullary loop and the endothelium of the descending vasa recta than that in the proximal tubule.At 6m of age: In the superficial cortex, the juncture of renal cortex and medulla, as well as the medulla, AQP1 was expressed at hige level.At 9m of age: The expression of AQP1 was weaker in the renal cortex, descending thin segment medullary loop and the endothelium of the descending vasa recta; the AQP1 immunoreactivity was decreased in intensity compared with the labeling at 6m of age.At 12m of age: The expression of AQP1 was weak in the renal cortex, and it was weaker the descending thin segment medullary loop and the endothelium of the descending vasa recta than that at 9m of age.At 15m of age: Weak AQP1 immunostaining was observed in the superficial cortex and the descending thin segment of medullary loop and the endothelium of the capillary of medullary loop at the corticomedullary junction, AQP1 was expressed in the proximal tubule. In the medulla, there was decreasing in the number of AQP1 positive in descending vasa recta after birth.At 18m of age: In the superficial cortex, at the corticomedullary junction, as well as the medulla, it was not almost obviously difference compared with at 15m of age. 3. Result of the AQP1 expression was quantitatively analyzed by a computerized densitometry:By one-way analysis of variance, statistical results about the expression of AQP1 quantitatively analyzed in the renal cortex and the renal medulla, as follow:A quantitative comparison of AQP1 expression in the cortex of kidney: It was decreased apparently that the expressive quantity of AQP1 at 7d, 14d, 21d, 28d of age after birth respectively were compared with at 1d after birth (P < 0.05) ;It was not difference apparently that the expressive quantity of AQP1 at 3m, 6m, 9m, 12m, 15m, and 18m of age after birth respectively was compared with at 1d after birth (P >0.05) . Expression quantity of AQP1 was maximal in the cortex at 6m of age. Expression quantities of AQP1 decreased gradually with development after 6th month of age.A quantitative comparison of AQP1 expression the renal medulla: It was decreased apparently that the expressive quantity of AQP1 at 7d, 14d, 21d, 28d and 3m of age after birth respectively was compared with 1d of age after birth (P < 0.05); It was not difference apparently that the expressive quantity of AQP1 at 6m of age were compared with 1d of age after brith (P > 0.05); It was decreased apparently that the expressive quantity of AQP1 at 9m, 12m, 15m, and 18m of age after birth respectively was compared with at 1d of age after birth (P < 0.05). Expression quantity of AQP1 was maximal in the renal medulla at 6m of age.A quantitative comparison of AQP1 between in the renal cortex and medulla in the same group rat: The expression of AQP1 in intensity in the renal medulla was more than that in the renal cortex at 7d, 14d, 21d, and 28d, 3m, 6m, 9m, 12m, 15m, 18m of age after birth.Conclusion:1. Positiveness expression of AQP1 was observedin postnatal rat kidney at any of the ages examined. The expressive quantity of AQP1 was decreasing gradually in 1-month-old. It was increasing after 1-month-old age. It was peak at 6-month-old age. It was stable tendency after this.2. Expression of AQP1 in renal medulla was stronglyer than in renal cortex of rat kidney.3. Mean density of AQP1 expression in renal cortex of rat existed regional difference. Expression of AQP1 in proximal convoluted tubule of superficial cortex of the kidney is weaker than deep cortex of kidney. It was suggested that water molecule reabsorption be stronger than that of surperficial cortex.4. Expression of AQP1 in the medella thin segment and vasa recta endothelial was the strongest in kidney. It was suggested that renal medella thin segment was mainly locality of water reabsorption in renal tubule.5. It was possible that AQP1 participate in reabsorbing organics in the glomerular filtrate of proximal tubule...