Intracellular pH

Putnam, Robert W.; Roos, Albert de

doi:10.1002/cphy.cp140109

Cited by 17 publications

(22 citation statements)

References 420 publications

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“…For instance, central chemoreceptors, in response to an appropriate stimulus (i.e., during an acid/base disturbance), should produce a large signal (i.e., a large change in pH i ), and this signal should be maintained for the entire duration of the stimulus. This is in contrast to nonchemoreceptors, which typically maintain a more constant pH i in the face of acid/base disturbances due to membranebound pH-regulating transporters (19). The following characteristics would allow central chemoreceptors to function in this manner: 1) a low ␤ int to maximize the change in pH i during acid/base disturbances, 2) the ability of pH i to closely track pH o , and 3) the lack of and/or inhibition of pH i -regulating mechanisms during acid/base disturbances.…”

Section: Discussionmentioning

confidence: 97%

Intracellular pH regulation in neurons from chemosensitive and nonchemosensitive areas of the medulla

Ritucci

Chambers-Kersh

Dean

et al. 1998

American Journal of Physiology-Regulatory, Integrative and Comp

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brain stem; central chemoreceptor; carbon dioxide; fluorescence imaging; respiration; Na ϩ /H ϩ exchange THE LEVEL OF CO 2 /H ϩ in the blood is carefully regulated by certain neurons in several areas of the medulla oblongata. These neurons are collectively known as central chemoreceptors. The areas in which these neurons are located are known as chemosensitive areas and include the ventrolateral medulla (VLM), the nucleus of the solitary tract (NTS), and the medullary raphe (16). It is hypothesized that an increased level of CO 2 /H ϩ stimulates the central chemoreceptors, which in turn, via the respiratory central pattern generator neurons (which they presumably innervate), increase ventilation (8). The stimulus to the central chemoreceptors has been the subject of much debate. It has been hypothesized that the stimulus may be an increase in molecular CO 2 , a decrease in extracellular pH (pH o ), a decrease in intracellular pH (pH i ), or a combination of any of the three (1,7,16,24,25,30). We have previously shown that both pH i and pH o may play a role in central chemosensitivity (22).It would seem logical that if a change in pH is the major signaling pathway by which central chemoreceptors monitor a change in blood CO 2 /H ϩ , the manner in which these cells respond to acid/base disturbances should be different from that of cells that are not chemoreceptors (nonchemoreceptors). In a previous study, we found that Na ϩ /H ϩ exchange is the only pH i -regulating mechanism involved during recovery from intracellular acidification in neurons from both chemosensitive (NTS and VLM) and nonchemosensitive [hypoglossal nucleus (Hyp) and inferior olive (IO)] areas of the medulla (22). We also found that neurons from chemosensitive areas (NTS and VLM) respond with a maintained intracellular acidification during hypercapnic acidosis, but exhibit pH i recovery during isohydric hypercapnia. This is in contrast to neurons from nonchemosensitive areas (Hyp and IO) that exhibit pH i recovery even during hypercapnic acidosis (22). These findings suggest that the Na ϩ /H ϩ exchanger is more easily inhibited by a decrease of pH o in neurons from chemosensitive areas versus nonchemosensitive areas.The major aim of the present study was to examine pH i regulation in greater detail in individual neurons from chemosensitive and nonchemosensitive areas of the medulla to investigate whether other differences in pH i regulation are present. It must be noted that these data are from neurons in known chemosensitive areas (16) but that the individual neurons themselves may or may not be chemoreceptors. Our data show the following: 1) intrinsic buffering power (␤ int ) is the same in all neurons tested; 2) removal of extracellular chloride at steady-state pH i results in intracellular alkalinization in all Hyp, IO, and VLM neurons but results in intracellular acidification in most NTS neurons, suggesting that Cl Ϫ /HCO 3 Ϫ exchange is present in all Hyp, IO, and VLM neurons but not in most NTS neurons; 3) steady-state pH i is more depende...

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Section: Discussionmentioning

confidence: 97%

Intracellular pH regulation in neurons from chemosensitive and nonchemosensitive areas of the medulla

Ritucci

Chambers-Kersh

Dean

et al. 1998

American Journal of Physiology-Regulatory, Integrative and Comp

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“…Only a few of these have been conducted in the presence of sustained and elevated CO 2 ; however, other studies using metabolic acid-base challenges are informative about the relationship between pH i and pH e . The general pattern shown in these studies is that (1) reducing pH e causes pH i to be reduced and (2) complete recovery of pH i does not occur until the starting pH e is re-established (Occhipinti and Boron, 2015;Putnam and Roos, 1997;Vaughan-Jones et al, 2009 ] to reduce pH e , the pH i of all cell types was reduced and only fully recovered following the return of pH e to control values (Salameh et al, 2014). Generally, in vitro studies indicate that acute changes in external or environmental pH will rapidly affect pH i .…”

Section: In Vitro Studiesmentioning

confidence: 89%

“…It is well known that absolute physiological pH values differ between species and between body compartments within species, and are affected by temperature (Rahn, 1974); however, within a given system, pH values are regulated within a relatively narrow range (Cameron, 1989;Heisler, 1984). Deviations from normal physiological pH values can affect molecular charge, altering the structure and function of proteins, lipids, carbohydrates and nucleic acids, and, ultimately, reducing whole-animal performance (Occhipinti and Boron, 2015;Putnam and Roos, 1997). The degree to which a pH change affects function depends on the system in question.…”

Section: Introductionmentioning

confidence: 99%

“…1B,D) Brauner and Baker, 2009;Shartau and Brauner, 2014). Although all cells have the capacity for some degree of pH i regulation (Occhipinti and Boron, 2015;Putnam and Roos, 1997;Vaughan-Jones et al, 2009), in animals that employ coupled pH regulation, cells cannot fully compensate for changes in pH i during a large sustained reduction in pH e .…”

Section: Introductionmentioning

confidence: 99%

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Preferential intracellular pH regulation: hypotheses and perspectives

Shartau

Baker

Crossley

et al. 2016

Journal of Experimental Biology

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The regulation of vertebrate acid-base balance during acute episodes of elevated internal P CO2 is typically characterized by extracellular pH ( pH e ) regulation. Changes in pH e are associated with qualitatively similar changes in intracellular tissue pH ( pH i ) as the two are typically coupled, referred to as 'coupled pH regulation'. However, not all vertebrates rely on coupled pH regulation; instead, some preferentially regulate pH i against severe and maintained reductions in pH e . Preferential pH i regulation has been identified in several adult fish species and an aquatic amphibian, but never in adult amniotes. Recently, common snapping turtles were observed to preferentially regulate pH i during development; the pattern of acid-base regulation in these species shifts from preferential pH i regulation in embryos to coupled pH regulation in adults. In this Commentary, we discuss the hypothesis that preferential pH i regulation may be a general strategy employed by vertebrate embryos in order to maintain acid-base homeostasis during severe acute acid-base disturbances. In adult vertebrates, the retention or loss of preferential pH i regulation may depend on selection pressures associated with the environment inhabited and/or the severity of acid-base regulatory challenges to which they are exposed. We also consider the idea that the retention of preferential pH i regulation into adulthood may have been a key event in vertebrate evolution, with implications for the invasion of freshwater habitats, the evolution of air breathing and the transition of vertebrates from water to land.

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“…For most fishes, short-term exposure to a P w co 2 of more than 2 kPa results in uncompensated acidosis (see Brauner and Baker 2009) that can be lethal, although the exact mechanism(s) of CO 2 toxicity are unknown (Putnam and Roos 1997). In contrast, white sturgeon Acipenser transmontanus are remarkably tolerant of elevated CO 2 and the associated blood acidosis, exhibiting morbidity only when exposed to ≥8-kPa P w co 2 (D. W. Baker and C. J.…”

Section: Introductionmentioning

confidence: 99%

Exceptional CO₂Tolerance in White Sturgeon (Acipenser transmontanus) Is Associated with Protection of Maximum Cardiac Performance during Hypercapnia In Situ

Baker¹,

Hanson²,

Farrell³

et al. 2011

Physiological and Biochemical Zoology

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This is an electronic version of an article that was published as: Baker, D.W., Hanson, L.M., Farrell, A.P., & Brauner, C.J. (2011). Exceptional CO2 tolerance in white sturgeon (Acipenser transmontanus) is associated with protection of maximum cardiac performance during hypercapnia in situ. ABSTRACTWhite sturgeon rank among the most CO 2 -tolerant fish species examined to date. We investigated whether this exceptional CO 2 tolerance extended to the heart, an organ generally viewed as acidosis intolerant. Maximum cardiac output (Q max ) and maximum cardiac power output (PO max ) were assessed using a working, perfused, in situ heart preparation. Exposure to a Pco 2 of 3 kPa for 20 min had no significant effect on maximum cardiac performance, while exposure to 6-kPa Pco 2 reduced heart rate, Q max , PO max , and rate of ventricular force generation (F O ) by 23%, 28%, 26%, and 18%, respectively; however, full recovery was observed in all these parameters upon return to control conditions. These modest impairments during exposure to 6-kPa Pco 2 were associated with partially compensated intracellular ventricular acidosis. Maximum adrenergic stimulation (500 nmol L Ϫ1 adrenaline) during 6-kPa Pco 2 protected maximum cardiac performance via increased inotropy (force of contraction) without affecting heart rate. Exposure to higher CO 2 levels associated with morbidity in vivo (i.e., 8-kPa Pco 2 ) induced arrhythmia and a reduction in stroke volume during power assessment. Clearly, white sturgeon hearts are able to increase cardiac performance during severe hypercapnia that is lethal to other fishes. Future work focusing on atypical aspects of sturgeon cardiac function, including the lack of chronotropic response to adrenergic stimulation during hypercapnia, is warranted.

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Intracellular pH

Abstract: The sections in this article are: Techniques pH‐Sensitive Microelectrodes pH‐Sensitive Fluorescent Indicators Nuclear Magnetic Resonance Spectroscopy Some Observations on Intracellular pH Transients Mechanisms of pH Regulation Physicochemical Buffers … Show more

Cited by 17 publications

References 420 publications

Intracellular pH regulation in neurons from chemosensitive and nonchemosensitive areas of the medulla

Intracellular pH regulation in neurons from chemosensitive and nonchemosensitive areas of the medulla

Preferential intracellular pH regulation: hypotheses and perspectives

Exceptional CO₂Tolerance in White Sturgeon (Acipenser transmontanus) Is Associated with Protection of Maximum Cardiac Performance during Hypercapnia In Situ

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Intracellular pH

Abstract: The sections in this article are: Techniques pH‐Sensitive Microelectrodes pH‐Sensitive Fluorescent Indicators Nuclear Magnetic Resonance Spectroscopy Some Observations on Intracellular pH Transients Mechanisms of pH Regulation Physicochemical Buffers … Show more

Cited by 17 publications

References 420 publications

Intracellular pH regulation in neurons from chemosensitive and nonchemosensitive areas of the medulla

Intracellular pH regulation in neurons from chemosensitive and nonchemosensitive areas of the medulla

Preferential intracellular pH regulation: hypotheses and perspectives

Exceptional CO2Tolerance in White Sturgeon (Acipenser transmontanus) Is Associated with Protection of Maximum Cardiac Performance during Hypercapnia In Situ

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Product

Resources

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Exceptional CO₂Tolerance in White Sturgeon (Acipenser transmontanus) Is Associated with Protection of Maximum Cardiac Performance during Hypercapnia In Situ