scholarly journals Intestinal bicarbonate secretion in Amphiuma measured by pH stat in vitro: relationship with metabolism and transport of sodium and chloride ions.

1981 ◽  
Vol 314 (1) ◽  
pp. 429-443 ◽  
Author(s):  
M A Imon ◽  
J F White
Keyword(s):  
Chloride Ions ◽  
Bicarbonate Secretion ◽  
Ph Stat

Bicarbonate secretion by rabbit proximal colon

1986 ◽  
Vol 251 (4) ◽  
pp. G436-G445 ◽  
Author(s):  
S. K. Sullivan ◽  
P. L. Smith
Keyword(s):  
Transport Process ◽  
Short Circuit ◽  
Proximal Colon ◽  
Bathing Solution ◽  
Bicarbonate Secretion ◽  
Rabbit Ileum ◽  
Ussing Chambers ◽  
Ph Stat ◽  
Dependent Mechanism

Stripped segments of proximal colon (1-6 cm distal to the ampulla caecalis coli) were studied in vitro in Ussing chambers under short-circuit conditions using the pH-stat technique. With glucose and HCO3-CO2 present in the serosal bathing solution only, proximal colon alkalinizes the luminal bathing solution at a rate of 2.1 +/- 0.2 mu eq X h-1 X cm-2 (n = 36). With HCO3-CO2 present in the luminal bathing solution alone, proximal colon does not significantly acidify or alkalinize the serosal bathing solution. Addition of glucose (10 mM) to the luminal bathing solution abolished luminal alkalinization. Removal of HCO3 and CO2 from the serosal bathing solution or replacement of O2 with N2 also abolished luminal alkalinization. Acetazolamide (0.1 mM) added to both bathing solutions did not alter the rate of luminal alkalinization. Ion-replacement studies revealed that the alkalinization process was highly dependent on the presence of Na in the bathing solutions and much less dependent on the presence of Cl. Furthermore, ouabain (0.1 mM) significantly reduced luminal alkalinization. As in rabbit ileum, serosal epinephrine (0.1 mM) did not alter luminal alkalinization but increased serosal alkalinization by a Na-dependent mechanism. These results suggest that luminal alkalinization results from a Na-dependent, active transcellular HCO3 transport process and that a Na-dependent HCO3 absorptive process is activated by adrenergic stimuli.

Regulation of bicarbonate transport in rabbit ileum: pH stat studies

1989 ◽  
Vol 257 (4) ◽  
pp. G607-G615 ◽  
Author(s):  
J. H. Sellin ◽  
R. Desoignie
Keyword(s):  
Short Circuit ◽  
Exchange Process ◽  
Short Circuit Current ◽  
Ringer Solution ◽  
Bicarbonate Transport ◽  
Bicarbonate Secretion ◽  
Acid Base Balance ◽  
Rabbit Ileum ◽  
Ph Stat

Although it is well recognized that the ileum secretes bicarbonate, understanding of the mechanisms of the transport of this ion has been limited by the inability to measure fluxes in vitro. However, by clamping the bathing fluid at a set pH using a pH stat system, accurate measurements of bicarbonate movement can be made. Bicarbonate transport in rabbit ileum in vitro was measured by simultaneously employing both the pH stat and short-circuit techniques. The role of acid-base balance was assessed by systematically altering buffer bicarbonate concentration, pH, and partial pressure of CO2 (PCO2). Bicarbonate secretion was strongly correlated with both serosal [HCO3-] (r = 0.824, P less than 0.01) and serosal pH (r = 0.793, P less than 0.01). Bicarbonate absorption was not significantly altered by mucosal [HCO3-], pH, or PCO2. Paracellular movement of bicarbonate, as assessed by voltage clamping and diffusion potential experiments, did not appear to be a major component of transcellular transport. Epinephrine stimulated bicarbonate absorption significantly, both in Cl-containing and Cl-free Ringer solution but did not alter bicarbonate secretion. Epinephrine-induced decreases in short-circuit current were correlated with enhanced bicarbonate absorption. Bicarbonate secretion was inhibited by serosal chloride and serosal bumetanide; mucosal chloride stimulated bicarbonate secretion. Mucosal chloride did not affect bicarbonate absorption. Glucocorticoids enhanced both bicarbonate absorption and secretion. These results suggest that there are discrete apical and basolateral transport mechanisms that regulate bicarbonate transport. Bicarbonate secretion may be mediated by a basolateral bumetanide-sensitive, chloride-inhibitable transporter and by an apical chloride-bicarbonate exchange process.

In vitro Lipolysis as a Tool for the Establishment of IVIVC for Lipid-Based Drug Delivery Systems

2019 ◽  
Vol 16 (8) ◽  
pp. 688-697
Author(s):  
Ravinder Verma ◽  
Deepak Kaushik
Keyword(s):  
Drug Delivery ◽  
Ph Value ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Rapid Screening ◽  
Resonance Spectroscopy ◽  
Fed State ◽  
In Vitro Lipolysis ◽  
Ph Stat

: In vitro lipolysis has emerged as a powerful tool in the development of in vitro in vivo correlation for Lipid-based Drug Delivery System (LbDDS). In vitro lipolysis possesses the ability to mimic the assimilation of LbDDS in the human biological system. The digestion medium for in vitro lipolysis commonly contains an aqueous buffer media, bile salts, phospholipids and sodium chloride. The concentrations of these compounds are defined by the physiological conditions prevailing in the fasted or fed state. The pH of the medium is monitored by a pH-sensitive electrode connected to a computercontrolled pH-stat device capable of maintaining a predefined pH value via titration with sodium hydroxide. Copenhagen, Monash and Jerusalem are used as different models for in vitro lipolysis studies. The most common approach used in evaluating the kinetics of lipolysis of emulsion-based encapsulation systems is the pH-stat titration technique. This is widely used in both the nutritional and the pharmacological research fields as a rapid screening tool. Analytical tools for the assessment of in vitro lipolysis include HPLC, GC, HPTLC, SEM, Cryo TEM, Electron paramagnetic resonance spectroscopy, Raman spectroscopy and Nanoparticle Tracking Analysis (NTA) for the characterization of the lipids and colloidal phases after digestion of lipids. Various researches have been carried out for the establishment of IVIVC by using in vitro lipolysis models. The current publication also presents an updated review of various researches in the field of in vitro lipolysis.

scholarly journals Effect of Propolis Preparations on Transepithelial Electrical Potential, Resistance, and Ion Transport in In Vitro Study

2019 ◽  
Vol 2019 ◽  
pp. 1-9
Author(s):  
Paulina Smyk ◽  
Iga Hołyńska-Iwan ◽  
Dorota Olszewska-Słonina
Keyword(s):  
Electrical Resistance ◽  
Ussing Chamber ◽  
Electrical Potential ◽  
In Vitro Study ◽  
Ethanol Extract ◽  
Ringer Solution ◽  
Chloride Ions ◽  
Propolis Extract ◽  
Ions Transport

Background. Propolis and its ethanol extract show positive germicidal, bacteriostatic, and anti-inflammatory antioxidants and regenerative properties after use on the surface of the skin. Propolis is in common use in production of cosmetics and in folk medicine. The influence of this resinous mixture on ion channels, channels located in skin cells membranes and skin electrical resistance, was not explained. Objective. The main aim of the study was the evaluation of electrophysiological skin parameters during mechanical and chemical-mechanical stimulation after use of ethanol extract of propolis and propolis ointment in comparison with iso-osmotic Ringer solution. Methods. Skin fragments were taken from white New Zealand rabbits and distributed into three experimental groups which were incubated in ethanol extract of propolis (EEP), propolis ointment, and Ringer solution. Then they were placed in a Ussing chamber to measure electrophysiological parameters values. Results. In this study the influence of EEP on changes in value of electrical potential during block of chloride ions transport at the same time was observed. Ethanol propolis extract dissolved in water increases the transepidermal sodium ions transport in contrast to propolis ointment. Conclusion. The way of preparation cosmetics, which contain propolis, has effects on transepidermal ions transport in the rabbit’s skin. The value of skin electrical resistance is changing with penetration depth of active propolis substances contained in cosmetics.

scholarly journals Ferroxidase activity of ferritin: effects of pH, buffer and Fe(II) and Fe(III) concentrations on Fe(II) autoxidation and ferroxidation

1999 ◽  
Vol 338 (3) ◽  
pp. 615-618 ◽  
Author(s):  
Xiaoke YANG ◽  
N. Dennis CHASTEEN
Keyword(s):  
Ph Control ◽  
Alternative Mechanism ◽  
Experimental Conditions ◽  
Iron Storage ◽  
Ferroxidase Activity ◽  
Effects Of Ph ◽  
Ph Stat ◽  
Ph Buffer ◽  
Horse Spleen Ferritin

It is widely accepted that iron deposition in the iron storage protein ferritin in vitro involves Fe(II) oxidation, and that ferritin facilitates this oxidation at a ferroxidase site on the protein. However, these views have recently been questioned, with the protein ferroxidase activity instead being attributed to autoxidation from the buffer alone. Ligand exchange between another protein with ferroxidase activity and ferritin has been proposed as an alternative mechanism for iron incorporation into ferritin. In the present work, a pH stat apparatus is used to eliminate the influence of buffers on iron(II) oxidation. Here we show that the recent experiments questioning the ferroxidase activity of ferritin were flawed by inadequate pH control, that buffers actually retard rather than facilitate iron(II) oxidation, and that horse spleen ferritin has ferroxidase activity when measured under proper experimental conditions. Furthermore, high pH (7.0), a high Fe(II) concentration and the presence of Fe(III) all favour Fe(II) autoxidation in the presence or absence of ferritin.

Protein kinase C potentiates cAMP-stimulated mouse duodenal mucosal bicarbonate secretion in vitro

2004 ◽  
Vol 286 (5) ◽  
pp. G814-G821 ◽  
Author(s):  
Bi-Guang Tuo ◽  
Jimmy Y. C. Chow ◽  
Kim E. Barrett ◽  
Jon I. Isenberg
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Duodenal Mucosa ◽  
Bicarbonate Secretion ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Ussing Chambers ◽  
Duodenal Bicarbonate Secretion

PKC has been shown to regulate epithelial Cl- secretion in a variety of models. However, the role of PKC in duodenal mucosal bicarbonate secretion is less clear. We aimed to investigate the role of PKC in regulation of duodenal mucosal bicarbonate secretion. Bicarbonate secretion by murine duodenal mucosa was examined in vitro in Ussing chambers using a pH-stat technique. PKC isoform expression and activity were assessed by Western blotting and in vitro kinase assays, respectively. PMA (an activator of PKC) alone had no effect on duodenal bicarbonate secretion or short-circuit current ( Isc). When PMA and dibutyryl-cAMP (db-cAMP) were added simultaneously, PMA failed to alter db-cAMP-stimulated duodenal bicarbonate secretion or Isc ( P > 0.05). However, a 1-h preincubation with PMA potentiated db-cAMP-stimulated duodenal bicarbonate secretion and Isc in a concentration-dependent manner (from 10-8 to 10-5M) ( P < 0.05). PMA preincubation had no effects on carbachol- or heat-stable toxin-stimulated bicarbonate secretion. Western blot analysis revealed that PKCα, -γ, -ϵ, -θ, -μ, and -ι/λ were expressed in murine duodenal mucosa. Ro 31–8220 (an inhibitor active against PKCϵ, -α, -β, and -γ), but not Gö 6983 (an inhibitor active against PKCα, -γ, -β, and -δ), reversed the potentiating effect of PMA on db-cAMP-stimulated bicarbonate secretion. PMA also time- and concentration-dependently increased the activity of PKCϵ, an effect that was prevented by Ro 31–8220 but not Gö 6983. These results demonstrate that activation of PKC potentiates cAMP-stimulated duodenal bicarbonate secretion, whereas it does not modify basal secretion. The effect of PKC on cAMP-stimulated bicarbonate secretion is mediated by the PKCϵ isoform.

scholarly journals Aldosterone up-regulates voltage-gated potassium currents and NKCC1 protein membrane fractions

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Parveen Bazard ◽  
Bo Ding ◽  
Harish K. Chittam ◽  
Xiaoxia Zhu ◽  
Thomas A. Parks ◽  
...  
Keyword(s):  
Protein Expression ◽  
Mineralocorticoid Receptor ◽  
Therapeutic Potential ◽  
Potassium Currents ◽  
Chloride Ions ◽  
Mrna Levels ◽  
Mineralocorticoid Receptor Antagonist ◽  
Voltage Gated ◽  
Age Related

Abstract Na+–K+–2Cl− Cotransporter (NKCC1) is a protein that aids in the active transport of sodium, potassium, and chloride ions across cell membranes. It has been shown that long-term systemic treatment with aldosterone (ALD) can enhance NKCC1 protein expression and activity in the aging cochlea resulting in improved hearing. In the present work, we used a cell line with confirmed NKCC1 expression to demonstrate that in vitro application of ALD increased outward voltage-gated potassium currents significantly, and simultaneously upregulated whole lysate and membrane portion NKCC1 protein expression. These ALD-induced changes were blocked by applying the mineralocorticoid receptor antagonist eplerenone. However, application of the NKCC1 inhibitor bumetanide or the potassium channel antagonist Tetraethyl ammonium had no effect. In addition, NKKC1 mRNA levels remained stable, indicating that ALD modulates NKCC1 protein expression via the activation of mineralocorticoid receptors and post-transcriptional modifications. Further, in vitro electrophysiology experiments, with ALD in the presence of NKCC1, K+ channel and mineralocorticoid receptor inhibitors, revealed interactions between NKCC1 and outward K+ channels, mediated by a mineralocorticoid receptor-ALD complex. These results provide evidence of the therapeutic potential of ALD for the prevention/treatment of inner ear disorders such as age-related hearing loss.

Characterization of an early afterhyperpolarization after a brief train of action potentials in rat hippocampal neurons in vitro

1990 ◽  
Vol 63 (1) ◽  
pp. 72-81 ◽  
Author(s):  
A. Williamson ◽  
B. E. Alger
Keyword(s):  
Action Potentials ◽  
Hippocampal Neurons ◽  
Pyramidal Cells ◽  
Chloride Ions ◽  
Membrane Potentials ◽  
Resting Potential ◽  
K Channel ◽  
Delayed Rectifier ◽  
Extracellular Potassium

1. In rat hippocampal pyramidal cells in vitro, a brief train of action potentials elicited by direct depolarizing current pulses injected through an intracellular recording electrode is followed by a medium-duration afterhyperpolarization (mAHP) and a longer, slow AHP. We studied the mAHP with the use of current-clamp techniques in the presence of dibutyryl cyclic adenosine 3',5'-monophosphate (cAMP) to block the slow AHP and isolate the mAHP. 2. The mAHP evoked at hyperpolarized membrane potentials was complicated by a potential generated by the anomalous rectifier current, IQ. The mAHP is insensitive to chloride ions (Cl-), whereas it is sensitive to the extracellular potassium concentration ([K+]o). 3. At slightly depolarized levels, the mAHP is partially Ca2+ dependent, being enhanced by increased [Ca2+]o and BAY K 8644 and depressed by decreased [Ca2+]o, nifedipine, and Cd2+. The Ca2(+)-dependent component of the mAHP was also reduced by 100 microM tetraethylammonium (TEA) and charybdotoxin (CTX), suggesting it is mediated by the voltage- and Ca2(+)-dependent K+ current, IC. 4. Most of the Ca2(+)-independent mAHP was blocked by carbachol, implying that IM plays a major role. In a few cells, a small Ca2(+)- and carbachol-insensitive mAHP component was detectable, and this component was blocked by 10 mM TEA, suggesting it was mediated by the delayed rectifier current, IK. The K+ channel antagonist 4-aminopyridine (4-AP, 500 microM) did not reduce the mAHP. 5. We infer that the mAHP is a complex potential due either to IQ or to the combined effects of IM and IC. The contributions of each current depend on the recording conditions, with IC playing a role when the cells are activated from depolarized potentials and IM dominating at the usual resting potential. IQ is principally responsible for the mAHP recorded at hyperpolarized membrane potentials.

scholarly journals Azaspiracids Increase Mitochondrial Dehydrogenases Activity in Hepatocytes: Involvement of Potassium and Chloride Ions

Marine Drugs ◽  
2019 ◽  
Vol 17 (5) ◽  
pp. 276 ◽  
Author(s):  
Marco Pelin ◽  
Jane Kilcoyne ◽  
Chiara Florio ◽  
Philipp Hess ◽  
Aurelia Tubaro ◽  
...  
Keyword(s):  
Chloride Channels ◽  
Gastrointestinal Symptoms ◽  
In Vitro Study ◽  
Chloride Ions ◽  
In Vivo Studies ◽  
The European Union ◽  
Channel Inhibition ◽  
Dehydrogenases Activity

Background: Azaspiracids (AZAs) are marine toxins that are produced by Azadinium and Amphidoma dinoflagellates that can contaminate edible shellfish inducing a foodborne poisoning in humans, which is characterized by gastrointestinal symptoms. Among these, AZA1, -2, and -3 are regulated in the European Union, being the most important in terms of occurrence and toxicity. In vivo studies in mice showed that, in addition to gastrointestinal effects, AZA1 induces liver alterations that are visible as a swollen organ, with the presence of hepatocellular fat droplets and vacuoles. Hence, an in vitro study was carried out to investigate the effects of AZA1, -2, and -3 on liver cells, using human non-tumor IHH hepatocytes. Results: The exposure of IHH cells to AZA1, -2, or -3 (5 × 10−12–1 × 10−7 M) for 24 h did not affect the cell viability and proliferation (Sulforhodamine B assay and 3H-Thymidine incorporation assay), but they induced a significant concentration-dependent increase of mitochondrial dehydrogenases activity (MTT reduction assay). This effect depends on the activity of mitochondrial electron transport chain complex I and II, being counteracted by rotenone and tenoyl trifluoroacetone, respectively. Furthermore, AZAs-increased mitochondrial dehydrogenase activity was almost totally suppressed in the K+-, Cl−-, and Na+-free media and sensitive to the specific inhibitors of KATP and hERG potassium channels, Na+/K+, ATPase, and cystic fibrosis transmembrane conductance regulator (CFTR) chloride channels. Conclusions: These results suggest that AZA mitochondrial effects in hepatocytes derive from an imbalance of intracellular levels of K+ and, in particular, Cl− ions, as demonstrated by the selective reduction of toxin effects by CFTR chloride channel inhibition.

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