Blog
About

0
views
0
recommends
+1 Recommend
1 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: found

      Cellular Localization of Aquaporin 7 in the Rat Kidney

      Read this article at

      ScienceOpenPublisherPubMed
      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          The cDNA for the seventh mammalian aquaporin (AQP7) was isolated from rat testis, and its expression was demonstrated at the tail of late spermatids [Ishibashi et al: J Biol Chem 1997;272:20782–20786]. AQP7 is also expressed in the kidney. The localization of AQP7 in the kidney is unknown. We examined the cellular localization of AQP7 in the kidney with Northern blot, reverse transcribed PCR, Western blot and immunohistochemistry in the rat kidney. In Northern blot, AQP7 was expressed in the cortex and the outer medulla but absent in the inner medulla of the kidney. Reverse transcribed PCR of rat nephron segments revealed the selective expression of AQP7 at the proximal straight tubules (PST). Western blot of the membrane fraction of outer medulla revealed a single band of ∼33 kDa. Immunohistochemistry of the rat kidney showed the selective expression of AQP7 at the brush border membranes of PST (S3 segment). AQP7 is now shown to be localized selectively at the brush border membranes of PST in the rat kidney. The result suggests that AQP7 may function as a pathway for transcellular water transport in PST in concert with more widely expressed AQP1 in proximal tubules. Alternatively, as AQP7 transports urea as well as water, AQP7 may function as a passive urea secretory pathway in this segment and may play a role in the formation and/or maintenance of the medullary urea concentration gradient.

          Related collections

          Most cited references 4

          • Record: found
          • Abstract: not found
          • Article: not found

          Electrical conductivity measurements from the GISP2 and GRIP Greenlandice cores

            Bookmark
            • Record: found
            • Abstract: found
            • Article: not found

            Severely impaired urinary concentrating ability in transgenic mice lacking aquaporin-1 water channels.

            Water channel aquaporin-1 (AQP1) is strongly expressed in kidney in proximal tubule and descending limb of Henle epithelia and in vasa recta endothelia. The grossly normal phenotype in human subjects deficient in AQP1 (Colton null blood group) and in AQP4 knockout mice has suggested that aquaporins (other than the vasopressin-regulated water channel AQP2) may not be important in mammalian physiology. We have generated transgenic mice lacking detectable AQP1 by targeted gene disruption. In kidney proximal tubule membrane vesicles from knockout mice, osmotic water permeability was reduced 8-fold compared with vesicles from wild-type mice. Although the knockout mice were grossly normal in terms of survival, physical appearance, and organ morphology, they became severely dehydrated and lethargic after water deprivation for 36 h. Body weight decreased by 35 +/- 2%, serum osmolality increased to >500 mOsm, and urinary osmolality (657 +/- 59 mOsm) did not change from that before water deprivation. In contrast, wild-type and heterozygous mice remained active after water deprivation, body weight decreased by 20-22%, serum osmolality remained normal (310-330 mOsm), and urine osmolality rose to >2500 mOsm. Urine [Na+] in water-deprived knockout mice was <10 mM, and urine osmolality was not increased by the V2 agonist DDAVP. The results suggest that AQP1 knockout mice are unable to create a hypertonic medullary interstitium by countercurrent multiplication. AQP1 is thus required for the formation of a concentrated urine by the kidney.
              Bookmark
              • Record: found
              • Abstract: found
              • Article: not found

              Cloning and functional expression of a new water channel abundantly expressed in the testis permeable to water, glycerol, and urea.

              A new member of the aquaporin (AQP) family has been identified from rat testis. This gene, referred as aquaporin 7 (AQP7), encodes a 269-amino acid protein that contained the conserved NPA motifs of MIP family proteins. AQP7 has the amino acid sequence homology with other aquaporins ( approximately 30%), and it is highest with AQP3 (48%), suggesting that both AQP3 and AQP7 belong to a subfamily in the MIP family. Injection of AQP7-cRNA into Xenopus oocytes expressed a 26-kDa protein detected by immunoblotting. The expression of AQP7 in oocytes stimulated the osmotic water permeability by 10-fold which was not inhibited by 0.3 mM mercury chloride. The Arrhenius activation energy for the stimulated water permeability was low (2.1 kcal/mol). AQP7 also facilitated glycerol and urea transport by 5- and 9-fold, respectively. The activation energy for glycerol was also low (5.3 kcal/mol after the correction of the endogenous glycerol permeability of oocytes). Northern blot analysis revealed a 1.5-kilobase pair transcript expressed abundantly in testis. In situ hybridization of testis revealed the expression of AQP7 at late spermatids in seminiferous tubules. The immunohistochemistry of testis localized the AQP7 expression at late spermatids and at maturing sperms. AQP7 may play an important role in sperm function.
                Bookmark

                Author and article information

                Journal
                EXN
                Nephron Exp Nephrol
                10.1159/issn.1660-2129
                Cardiorenal Medicine
                S. Karger AG
                1660-2129
                2000
                October 2000
                31 July 2000
                : 8
                : 4-5
                : 252-257
                Affiliations
                aDepartment of Pharmacology, Jichi Medical School, Minamikawachi, Tochigi, and bSecond Department of Internal Medicine, Tokyo Medical and Dental University, Tokyo, Japan
                Article
                20676 Exp Nephrol 2000;8:252–257
                10.1159/000020676
                10940724
                © 2000 S. Karger AG, Basel

                Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                Page count
                Figures: 4, References: 25, Pages: 6
                Product
                Self URI (application/pdf): https://www.karger.com/Article/Pdf/20676
                Categories
                Original Paper

                Comments

                Comment on this article