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During the congress, E-Posters will be accessible to all participants on the congress website 24/7, as well as in the E-poster stations in the congress center.
Preparing your E-Poster
Please review the E-Poster format requirements carefully when preparing your E-Poster. Should your E-Poster not meet the mentioned requirements, it may not be displayed as described above.
E-Poster Submission Deadline
Please prepare and upload your E-Poster no later than March 14, 2026 11.59PM CET. After this date, you will no longer be able to prepare and upload your E-poster and it will not be displayed and accessible on the congress website.
Please follow the instructions below to input your abstract title.
Abstract titles should be brief and reflect the content of the abstract.
In teleost fish, the kidneys play an important role in maintaining body fluid homeostasis. In the kidneys, the volume and the composition of the urine is regulated differently in seawater and freshwater fishes. The kidneys of seawater fish act as excretory organs for sulfate and magnesium, producing isotonic urine rich in these ions. In seawater fishes, the collecting ducts reabsorb Na+, Cl–, and water and reduce the volume of urine. Fish inhabiting hypoosmotic environments, such as freshwater or brackish water, have kidneys that produce and excrete large volumes of hypotonic urine. These fish reabsorb Na+ and Cl–, but not water, in the distal part of the renal tubules, including the distal tubules and collecting ducts. Euryhaline fish can live in both environments by regulating the water reabsorption in the collecting ducts. The water permeability of mammalian collecting ducts is regulated by aquaporin 2 (AQP2), which is expressed in the apical membrane. However, the molecular basis regulating water permeability in fish collecting ducts remains unclear since the Aqp2 gene is tetrapod-specific and absent in fish. In this study, we analyzed the expression and localization of Aqps in the collecting ducts of the Japanese pufferfish (Takifugu rubripes), a species that can live in both seawater and brackish water. We identified the Aqps responsible for regulating water reabsorption in fish collecting ducts.
The mRNA levels of Aqp genes (aqps) were quantified by quantitative PCR in the collecting ducts and whole kidney of Japanese pufferfish reared in seawater (35‰) or brackish water (1‰). Polyclonal antibodies were produced against Japanese pufferfish Aqp1a and Aqp4. Immunohistochemistry was performed on frozen sections of the pufferfish kidneys using these antibodies, and the fluorescence was detected by confocal microscopy.
In the whole kidney of the pufferfish, aqp1a, aqp1b, aqp4, and aqp8 exhibited high levels of expression, with aqp1a and aqp4 being most highly expressed in the collecting ducts. In the collecting ducts, the expression of aqp1a was significantly decreased and aqp4 was slightly decreased in the brackish water group compared to the seawater group. Immunohistochemical analysis using an anti-Aqp1a antibody showed staining of the apical membrane of renal collecting duct cells in the seawater pufferfish. The signal exhibited a substantial decrease in the brackish water pufferfish. Immunohistochemistry using an anti-Aqp4 antibody revealed clear signals in the basolateral membrane of renal collecting duct epithelial cells in both seawater and brackish water pufferfish.
In the seawater pufferfish collecting duct, Aqp1a and Aqp4, located in the apical and basolateral membranes, respectively, were suggested to be the primary pathways for water reabsorption. Furthermore, the absence of Aqp1a in the apical membrane of the brackish water pufferfish collecting duct was suggested to contribute to the production of hypotonic urine.
