title: Reciprocity in the developmental regulation of aquaporins 1, 3 and 5 during pregnancy and lactation in the rat.
abstract: Milk secretion involves significant flux of water, driven largely by synthesis of lactose within the Golgi apparatus. It has not been determined whether this flux is simply a passive consequence of the osmotic potential between cytosol and Golgi, or whether it involves regulated flow. Aquaporins (AQPs) are membrane water channels that regulate water flux. AQP1, AQP3 and AQP5 have previously been detected in mammary tissue, but evidence of developmental regulation (altered expression according to the developmental and physiological state of the mammary gland) is lacking and their cellular/subcellular location is not well understood. In this paper we present evidence of developmental regulation of all three of these AQPs. Further, there was evidence of reciprocity since expression of the rather abundant AQP3 and less abundant AQP1 increased significantly from pregnancy into lactation, whereas expression of the least abundant AQP5 decreased. It would be tempting to suggest that AQP3 and AQP1 are involved in the secretion of water into milk. Paradoxically, however, it was AQP5 that demonstrated most evidence of expression located at the apical (secretory) membrane. The possibility is discussed that AQP5 is synthesized during pregnancy as a stable protein that functions to regulate water secretion during lactation. AQP3 was identified primarily at the basal and lateral membranes of the secretory cells, suggesting a possible involvement in regulated uptake of water and glycerol. AQP1 was identified primarily at the capillary and secretory cell cytoplasmic level and may again be more concerned with uptake and hence milk synthesis, rather than secretion. The fact that expression was developmentally regulated supports, but does not prove, a regulatory involvement of AQPs in water flux through the milk secretory cell.
authors.affiliation: Department of Veterinary Clinical and Animal Sciences (IKVH) Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Sasan
authors.initials: S
authors.lastname: Nazemi
authors.affiliation: Department of Veterinary Clinical and Animal Sciences (IKVH) Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Mette
authors.initials: M
authors.lastname: Rahbek
authors.affiliation: Centre for Pharmaceutical Nanotechnology and Nanotoxicology, Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Ladan
authors.initials: L
authors.lastname: Parhamifar
authors.affiliation: Centre for Pharmaceutical Nanotechnology and Nanotoxicology, Department of Pharmacy, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Seyed Moein
authors.initials: SM
authors.lastname: Moghimi
authors.affiliation: Department of Food Sciences, Spectroscopy and Chemometrics section, Faculty of Science, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Hamid
authors.initials: H
authors.lastname: Babamoradi
authors.affiliation: Department of Veterinary Disease Biology (IVS), Parasitology and Aquatic Diseases, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Foojan
authors.initials: F
authors.lastname: Mehrdana
authors.affiliation: Department of Veterinary Clinical and Animal Sciences (IKVH) Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Dan Arne
authors.initials: DA
authors.lastname: Klærke
authors.affiliation: Department of Veterinary Clinical and Animal Sciences (IKVH) Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Christopher H
authors.initials: CH
authors.lastname: Knight
mesh_terms: D000818:Animals; D051398:Aquaporin 1 / Q000096:biosynthesis*; D051400:Aquaporin 3 / Q000096:biosynthesis*; D051402:Aquaporin 5 / Q000096:biosynthesis*; D002462:Cell Membrane / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology; D007774:Lactation / Q000378:metabolism*; D008321:Mammary Glands, Animal / Q000378:metabolism*; D008892:Milk / Q000378:metabolism; D011247:Pregnancy / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014867:Water / Q000378:metabolism
chemical_list: C496022:Aqp1 protein, rat; C496029:Aqp3 protein, rat; C496040:Aqp5 protein, rat; D051402:Aquaporin 5; D014867:Water; D051398:Aquaporin 1; D051400:Aquaporin 3