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Renal Disease; Fluid and Electrolyte Disorders
Published in John S. Axford, Chris A. O'Callaghan, Medicine for Finals and Beyond, 2023
Unlike many ions and molecules, water cannot be pumped directly in the body. Instead, water moves between sites by osmosis if there is an osmotic gradient and if the barrier separating the two sites contains pores or channels through which it can pass. Aquaporin molecules form water channels in most cell membranes. Intra- and extracellular fluid compartments are normally in approximate osmotic equilibrium. The Na+/K+ATPase pumps sodium out of cells and potassium into cells so: Intracellular fluid has high potassium and low sodium concentrations.Extracellular fluid has low potassium and high sodium concentrations.
Hyponatremia in pregnancy
Published in Nadia Barghouthi, Jessica Perini, Endocrine Diseases in Pregnancy and the Postpartum Period, 2021
Anthony Parravani, Bethany Pellegrino
Nonpregnant state, maintenance of serum osmolality and sodium:Under nonpregnant conditions, serum osmolality is maintained within a narrow range of 275–295 mOsm/L.Any changes in serum osmolality are sensed by osmoreceptors which respond to correct the change.An increase in serum osmolality by 1–2% results in the release of ADH from the posterior pituitary, which acts on the Arginine Vasopressin Receptor 2 (AVPR2) on the basolateral membrane of the collecting ducts in the kidneys. This leads to the upregulation of aquaporin 2 channels and increased water absorption by the kidneys.Any increase in serum osmolality also stimulates the thirst center in the hypothalamus, resulting in water intake to assist in correction of the hypertonic state.4
Anatomical and Physiological Changes in Pregnancy
Published in Karl H. Pang, Nadir I. Osman, James W.F. Catto, Christopher R. Chapple, Basic Urological Sciences, 2021
Joanna Shepherd, Stephen Radley
Arterial underfilling (despite the increase in plasma volume) stimulates arterial baroreceptors, leading to the activation of RAA and sympathetic nervous systems:Anti-diuretic hormone (ADH) from the hypothalamus increases.ADH acts on the collecting tubules:Mobilisation of aquaporins.Water reabsorption from urine into the bloodstream.Overall hypo-osmolar, hypervolemic state.
Therapeutic effects of Bombax ceiba flower aqueous extracts against loperamide-induced constipation in mice
Published in Pharmaceutical Biology, 2023
Liuping Wang, Shiyuan Xie, Xuan Jiang, Caini Xu, Youqiong Wang, Jianfang Feng, Bin Yang
Aquaporins are mainly expressed in the intestinal canal (Sun et al. 2020), which mediate the passive transport of free water across biofilm, thereby maintaining the homeostasis of the intracellular and extracellular environment (Matsuzaki et al. 2004). Moreover, the abnormal expression of aquaporins in the gastrointestinal tract is related to the occurrence of some diseases, such as constipation, gastritis, diarrhoea and gastric cancer (Liu et al. 2020). AQP3 is an important aquaporin located in the colon and is permeable to water (Li and Wang 2017). Previously studies have revealed the relationship between AQP3 and constipation, particularly morphine-induced constipation (Kon et al. 2015), promotes AQP3 expression level in the colon and subsequently increases water absorption from the luminal side to vasculature, which dries and hardens stool (Ikarashi et al. 2016). In the present study, the expression level of AQP3 was detected and the results showed that phenolphthalein and BCE relieve the symptoms of loperamide-induced constipation by decreasing the level of AQP3 in the colon of mice. However, the precise mechanisms remain to be further elucidated.
Anti-cataract therapies: is there a need for a new approach based on targeting of aquaporins?
Published in Expert Opinion on Therapeutic Targets, 2021
An important class of lens proteins, which are far lower in proportion that the crystallins, but which play a vital role in water transport, microcirculation and homeostasis in protein/water balance in the lens are the aquaporins [21]. Aquaporins are small membrane proteins found in a number of tissues in humans and animals. The three main aquaporins that are expressed in the human lens are aquaporin 0, 1, and 5 [21]. These aquaporins are water transporting proteins [22]. Aquaporin 0 (also known as Membrane Intrinsic Protein) is found in the fiber cells throughout the lens, constituting over half of the protein concentration of the cell membranes [22]. Aquaporin 1 is found in the epithelial cells [22] and aquaporin 5 has been detected in all parts of the lens [23] and is the second most prevalent of the aquaporins in mature lens fiber cells [23]. Aquaporin 7, an aquaglyceroporin which facilitates transport of small molecules as well as water and may be active in transport of nutrients, has also been detected in the eye lens epithelium [22]; it has a significantly lower water permeability than aquaporin 1 [24].
Mesenchymal stromal cells for ocular surface repair
Published in Expert Opinion on Biological Therapy, 2019
Olla Al-Jaibaji, Stephen Swioklo, Che J. Connon
Another common corneal disease is dry eye syndrome (DES). DES is a multifactorial disease of the cornea where the eye cannot produce lacrimal fluid and/or lacrimal fluid evaporates quickly, leading to drying, swelling, irritation, and reddening of the eye [44,45]. Ocular surface inflammation is the main cause of DES. Current treatments include lubricating eye drops and anti-inflammatory remedies [46]. As detailed above, it is clear that MSCs have anti-inflammatory effects on the cornea, therefore, it is a natural progression to investigate the benefits of MSCs on DES [47,48]. MSCs’ anti-inflammatory effects were tested in an in vivo murine model, where MSCs were found to suppress inflammation via the reduction of CD4+ T cell infiltration and inflammatory cytokines [49]. Another study used topically administered rat MSCs labeled with bromodeoxyuridine into DES-induced corneas to see MSC fate after injection. The authors found MSCs reduced inflammation and improved tear production [50]. Interestingly, MSCs were shown to engraft within the conjunctival epithelium and Meibomian glands, which aided in reducing inflammation. However, it was not determined whether this function was arbitrated by topically injected MSCs’ differentiation and production of trophic factors. Another in vivo study showed that MSCs can decrease inflammation and improve tear production via decrease in the lymphocyte foci size and an increase in aquaporin 5 level [51]. Aquaporin 5 is a protein that plays an important role in tear, pulmonary and saliva secretion. Thus, aquaporin production is directly involved in the maintenance of corneal health.