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KMID : 0381920070370040271
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Korean Journal of Microscopy
2007 Volume.37 No. 4 p.271 ~ p.280
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Renal Expression of TonEBP and Urea Transporter in the Water-deprived Mongolian Gerbil (Meriones unguiculatus)
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Park Yong-Deok
Kim Sung-Joong
Jung Ju-Young
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Abstract
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Tonicity-responsive enhancer binding protein (TonEBP) is a transcriptional factor essential in the function and development of the renal medulla. TonEBP plays a critical role in protecting renal medullary cells from the deleterious effect of hypertonicity. TonEBP is a key regulator of urinary concentration via stimulation of transcription of urea transporter (UT) in a manner independent of vasopressin. UT in the renal inner medulla is important for the conservation of body water due to its role in the urine concentrating mechanism. Mongolian gerbil (Meriones unguiculatus) has been as an model animal for studying the neurological disease such as stroke and epilepsy because of the congenital incomplete in Willis circle, as well as the investigation of water metabolism because of the long time-survival in the condition of water-deprived desert condition, compared with other species animal. In this study, we divide 3 groups of which each group include the 5 animals. In the study of 7 or 14 days water restricted condition, we investigated the TonEBP and UT-A by using a immunohistochemistry in the kidney. In the normal kidney, the distribution of TonEBP is generally localized on
nuclei of inner medullary cells. Nuclear distribution of TonEBP is generally increased throughout the medulla in 7 and 14 days dehydrated group compared with control group. Increased nuclear localization was particularly dramatic in thin limbs. In control groups, UT-A was expressed in inner stripe of outer medulla (ISOM) and inner medulla (IM). UT-A was present in the terminal part of the short-loop of descending thin limbs (DTL) in ISOM and also present in the inner medullary collecting duct (IMCD), where the intensity of it gradually increased toward the papillary tip. In the dehydrated kidney, UT-A immunoreactivity was increased in the short-loop of DTL in ISOM and in the long-loop of DTL in the initial part of IM, where was expressed moderate positive reaction in the normal kidney. Also it was up regulated in the IMCD in initial & middle part of IM. However UT-A down regulated in the IMCD, where the intensity of it gradually decreased toward the papillary tip. These findings suggest that increased levels of TonEBP in medulla and UT-A in shot-loop of DTL and IMCD play a important role for maintain fluid balance in the water-deprived mongolian gerbil kidney.
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KEYWORD
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TonEBP, UT-A, Immunohistochemistry, Mongolian gerbil, Kidney
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