Freeze Fracture in Lung Research
Joan Gil in Models of Lung Disease, 2020
Further specialized membrane structures include orthogonal arrays of particles (OAP) that have been observed in the basal plasma membrane of pneumocytes in turtles and frogs and in human type I pneumocytes (Bartels and Miragall, 1986). Such orthogonal arrays appeared to be absent from pneumocytes in other mammalian species, but were present in the basal plasma membrane of airway epithelial cells in a variety of species (Inoue and Hogg, 1977; Gordon, 1985). The number of particles per OPA ranged from 4 to 40 in lower vertebrates and from 4 to 24 in humans (Bartels and Miragall, 1986). It is interesting that their number appeared to increase substantially following acute or chronic exposure to NO2 (Gordon, 1985). Although a possible role in the regulation of ion transport has been suggested, their function is at present unclear.
Cell Components and Function
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal in Principles of Physiology for the Anaesthetist, 2020
Ion channels are membrane-spanning proteins that form pores that allow ion transport. These channels are selective and conduct ions across electrochemical gradients at a high rate. External signals cause ion channels to undergo conformational changes. Depending on the signal, the ion channels may ‘open’ or ‘close’, a process called gating. The gate is a region of the protein channel that prevents ion flow in the closed state. Ion channels may be (i) ligand-gated (gating mediated by a neurotransmitter or chemical binding to sensor region of the channel), (ii) voltage-gated (membrane potential changes near channel) or (iii) mechanosensitive (activation by pressure, stretch or temperature).
Classes of Compounds with GI Tract Toxicity
Shayne C. Gad in Toxicology of the Gastrointestinal Tract, 2018
Slow-K is an extended-release wax core oral tablet used to treat patients suffering from potassium depletion. Potassium ion (K+) is an essential intracellular cation for most body tissues. This ion is vital to maintain intracellular tonicity and normal renal function, transmission of nerve impulses, and contraction of smooth, cardiac, and skeletal muscles. The intracellular concentration of K+ is approximately 150–160 mEq/L (Ohtsu, 1956; Worth, 1988). Normally, plasma potassium concentrations in adult humans range from 3.5 to 5 mEq/L (Worth, 1988). An active ion transport system maintains this gradient across the plasma membrane.
An overview of carbonic anhydrases and membrane channels of synoviocytes in inflamed joints
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2019
Currently, experimental evidence for the involvement of CAs and FLS membrane channels in RA is limited. The physiological and pathological roles of ion channels and transporters in dynamic FLS migration have not yet been studied in detail. Here, we have summarised the studies on membrane channels and regulatory enzymes of RA-FLS with an aim to understand their migrated state. However, many questions regarding RA-FLS still need to be clarified. What are the exact molecular mechanisms by which ion transporter affects the FLS migration apparatus? What are the exact components of synovial fluid that mediate the FLS dynamics? What are the components affecting the differential expression of CAs and membrane channels in FLS? What is the combined mechanism of CAs as regulatory enzymes? Several membrane channels and transporters show tissue-specific expression. Thus, unravelling the mechanisms by which ion channels and transporters are positioned in and modulate the migration of activated FLS will be a rewarding pursuit for the coming years. The motivation of channel physiologists is also needed to develop potential therapeutics to counter the critical pathophysiological involvement of FLS migration in joints in RA.
Solanaceae glycoalkaloids: α-solanine and α-chaconine modify the cardioinhibitory activity of verapamil
Published in Pharmaceutical Biology, 2022
Szymon Chowański, Magdalena Winkiel, Monika Szymczak-Cendlak, Paweł Marciniak, Dominika Mańczak, Karolina Walkowiak-Nowicka, Marta Spochacz, Sabino A. Bufo, Laura Scrano, Zbigniew Adamski
Nevertheless, SGAs affect not only passive but also active ion transport. For example, α-solanine was found to inhibit active calcium transport in a rat duodenum (Michalska et al. 1985), and α-chaconine or α-solanine decreased the transepithelial active transport of sodium ions in frog skin (Blankemeyer et al. 1995, 1997). Moreover, the above data suggest that SGAs might act both in channels ion transporter-dependent and ion transporter-independent ways. Moreover, SGAs interact with cell membrane cholesterol. α-Solanine and α-chaconine can form tubular structures within cell membrane monolayers in artificial phospholipid vesicles, increasing the permeability of membrane structures for different ions (Keukens et al. 1995, 1996). Thus, the effects of SGAs on ion balance might change the cell membrane potential and thus modulate the activity of excitable cells, including myocardial cells. Blankemeyer et al. (1998) showed that solasonine and solamargine decrease the cell membrane potential (hyperpolarization) in frog embryo cells. If the same occurs in myocardial cells, it could explain the cardioinhibitory properties of SGAs.
In vitro study of the effects of DC electric fields on cell activities and gene expression in human choriocarcinoma cells
Published in Electromagnetic Biology and Medicine, 2021
Jinxin Chen, Linbo Guan, Ping Fan, Xinghui Liu, Rui Liu, Yu Liu, Huai Bai
All cell types and intracellular organelles maintain transmembrane electrical potentials owing to asymmetric ion transport. For instance, in human adipose tissue-derived stem cells, there are channels for a Ca2+-activated k+ current, transient outward k+ current, delayed rectifier-like k+ current, and tetrodotoxin-sensitive transient inward Na+ current (Bai et al. 2007). In trophoblast cells, there are several types of molecules on the cell membrane that may be associated with TEP production. These molecules include Na-K pumps (Na-K ATPase) and Na-H exchangers. Based on the above reports and the present finding that choriocarcinoma cells are responsive to EF signals, we speculate that EF might exert a profound influence on the choriocarcinoma cell function via direct activation of ion channels.
Related Knowledge Centers
- Atp Synthase
- Facilitated Diffusion
- Transmembrane Protein
- Ion Channel
- Passive Transport
- Biological Membrane
- Adenosine Triphosphate
- Redox
- Ion Transporter Superfamily
- Membrane Transport Protein