Intestinal fluid absorption in anadromous salmonids: importance of tight junctions and aquaporins
The anadromous salmonid life cycle includes both fresh water (FW) and seawater (SW) stages. The parr-smolt transformation (smoltification) pre–adapt the fish to SW while still in FW. The osmoregulatory organs change their mode of action from a role of preventing water inflow in FW, to absorb ions to...
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2012-09-01
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| Series: | Frontiers in Physiology |
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| Online Access: | http://journal.frontiersin.org/Journal/10.3389/fphys.2012.00388/full |
| _version_ | 1819000438752542720 |
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| author | Kristina eSundell Henrik eSundh |
| author_facet | Kristina eSundell Henrik eSundh |
| author_sort | Kristina eSundell |
| collection | DOAJ |
| description | The anadromous salmonid life cycle includes both fresh water (FW) and seawater (SW) stages. The parr-smolt transformation (smoltification) pre–adapt the fish to SW while still in FW. The osmoregulatory organs change their mode of action from a role of preventing water inflow in FW, to absorb ions to replace water lost by osmosis in SW. During smoltification, the drinking rate increases, in the intestine the ion and fluid transport increases and is further elevated after SW entry. In SW, the intestine absorbs ions to create an inwardly directed water flow which is accomplished by increased Na+,K+-ATPase (NKA) activity in the basolateral membrane, driving ion absorption via ion channels and/or co-transporters. This review will aim at discussing the expression patterns of the ion transporting proteins involved in intestinal fluid absorption in the FW stage, during smoltification and after SW entry. Of equal importance for intestinal fluid absorption as the active absorption of ions, is the permeability of the epithelium to ions and water. During the smoltification the increase in NKA activity and water uptake in SW is accompanied by decreased paracellular permeability suggesting a redirection of the fluid movement from a paracellular route in FW, to a transcellular route in SW. Increased transcellular fluid absorption could be achieved by incorporation of aquaporins (AQPs) into the enterocyte membranes and/or by a change in fatty acid profile of the enterocyte lipid bilayer. An increased incorporation of unsaturated fatty acids into the membrane phospholipids will increase water permeability by enhancing the fluidity of the membrane. A second aim of the present review is therefore to discuss the presence and regulation of expression of AQPs in the enterocyte membrane as well as to discuss the profile of fatty acids present in the membrane phospholipids during different stages of the salmonid lifecycle. |
| first_indexed | 2024-12-20T22:33:19Z |
| format | Article |
| id | doaj.art-2f551948b5964d108038aed9638b6498 |
| institution | Directory Open Access Journal |
| issn | 1664-042X |
| language | English |
| last_indexed | 2024-12-20T22:33:19Z |
| publishDate | 2012-09-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Physiology |
| spelling | doaj.art-2f551948b5964d108038aed9638b64982022-12-21T19:24:41ZengFrontiers Media S.A.Frontiers in Physiology1664-042X2012-09-01310.3389/fphys.2012.0038831740Intestinal fluid absorption in anadromous salmonids: importance of tight junctions and aquaporinsKristina eSundell0Henrik eSundh1University of GothenburgUniversity of GothenburgThe anadromous salmonid life cycle includes both fresh water (FW) and seawater (SW) stages. The parr-smolt transformation (smoltification) pre–adapt the fish to SW while still in FW. The osmoregulatory organs change their mode of action from a role of preventing water inflow in FW, to absorb ions to replace water lost by osmosis in SW. During smoltification, the drinking rate increases, in the intestine the ion and fluid transport increases and is further elevated after SW entry. In SW, the intestine absorbs ions to create an inwardly directed water flow which is accomplished by increased Na+,K+-ATPase (NKA) activity in the basolateral membrane, driving ion absorption via ion channels and/or co-transporters. This review will aim at discussing the expression patterns of the ion transporting proteins involved in intestinal fluid absorption in the FW stage, during smoltification and after SW entry. Of equal importance for intestinal fluid absorption as the active absorption of ions, is the permeability of the epithelium to ions and water. During the smoltification the increase in NKA activity and water uptake in SW is accompanied by decreased paracellular permeability suggesting a redirection of the fluid movement from a paracellular route in FW, to a transcellular route in SW. Increased transcellular fluid absorption could be achieved by incorporation of aquaporins (AQPs) into the enterocyte membranes and/or by a change in fatty acid profile of the enterocyte lipid bilayer. An increased incorporation of unsaturated fatty acids into the membrane phospholipids will increase water permeability by enhancing the fluidity of the membrane. A second aim of the present review is therefore to discuss the presence and regulation of expression of AQPs in the enterocyte membrane as well as to discuss the profile of fatty acids present in the membrane phospholipids during different stages of the salmonid lifecycle.http://journal.frontiersin.org/Journal/10.3389/fphys.2012.00388/fullaquaporinosmoregulationintestinal fluid absorptionclaudinparacellular permeabilitysalmonids |
| spellingShingle | Kristina eSundell Henrik eSundh Intestinal fluid absorption in anadromous salmonids: importance of tight junctions and aquaporins Frontiers in Physiology aquaporin osmoregulation intestinal fluid absorption claudin paracellular permeability salmonids |
| title | Intestinal fluid absorption in anadromous salmonids: importance of tight junctions and aquaporins |
| title_full | Intestinal fluid absorption in anadromous salmonids: importance of tight junctions and aquaporins |
| title_fullStr | Intestinal fluid absorption in anadromous salmonids: importance of tight junctions and aquaporins |
| title_full_unstemmed | Intestinal fluid absorption in anadromous salmonids: importance of tight junctions and aquaporins |
| title_short | Intestinal fluid absorption in anadromous salmonids: importance of tight junctions and aquaporins |
| title_sort | intestinal fluid absorption in anadromous salmonids importance of tight junctions and aquaporins |
| topic | aquaporin osmoregulation intestinal fluid absorption claudin paracellular permeability salmonids |
| url | http://journal.frontiersin.org/Journal/10.3389/fphys.2012.00388/full |
| work_keys_str_mv | AT kristinaesundell intestinalfluidabsorptioninanadromoussalmonidsimportanceoftightjunctionsandaquaporins AT henrikesundh intestinalfluidabsorptioninanadromoussalmonidsimportanceoftightjunctionsandaquaporins |