Effects of bicarbonate on resting potentials in mammalian skeletal muscle

Grossie, J.

doi:10.1002/jcp.1041250115

Cited by 3 publications

(8 citation statements)

References 26 publications

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“…As shown previously (Grossie, 1985), the removal of CO2/HCO3 is followed by a depolarization which is enhanced at 30~ and expectedly tends to be aggravated by dual impalement. The lower Vm was considered a complicating factor for interpretation of a subsequent acid pulse.…”

Section: Discussionmentioning

confidence: 70%

“…Above this range, the Na-H exchanger operates at a rate so low as to be negligible, whereas the Na/HCO3-C1 exchanger raises pHi to maintain a value of about 7.2. This model explains most of the observed pHi transients as well as providing a physiological basis for the finding that internal C1 activity in Edl muscle is less than that predicted by a passive distribution and definitely appears to be controlled, in part, by external HCO3 (Grossie, 1985).…”

Section: Discussionmentioning

confidence: 86%

“…Amiloride is known to inhibit both a Naconductive pathway and the Na-H antiport systems in various epithelial cells and it is important that, generally, much higher concentrations are required to inhibit the Na-H exchange pathway than the conductive pathway (Benos, 1982). In Edl muscle, CI is passively driven inward (Grossie, 1985) while HCO3 is directed outward. Therefore, an alkalizing HCOs-C1 exchange is not possible unless an active transport system exists.…”

Section: Discussionmentioning

confidence: 99%

“…Present interest in the mode of pHi regulation in this muscle was prompted by several other studies. The resting potential (Vm) in extensor digitorum longus (Edl) muscle from ketoacidotic diabetic rats was significantly depolarized but repolarized to nearly normal upon removal of CI, (Grossie, 1985) while Vm in soleus muscle from the same type of animal was normal (Paulus & Grossie, 1983). Experiments on normal Edl muscle showed that in the absence of external HCO3, Vm becomes more positive due in part to increases in internal Na and C1 (Grossie, 1985).…”

Section: Introductionmentioning

confidence: 99%

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Bicarbonate and fast-twitch muscle: Evidence for a major role in pH regulation

1988

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Internal pH (pHi) was analyzed in rat extensor digitorum longus (Edl) muscle at 30 degrees C with single-barrel liquid ion-selective electrodes. Average pHi in 284 cells was 7.197 +/- 0.006. Increases in CO2 from nominally 0 to 5% produced an acidification from which recovery took place. In different groups of cells, recovery from the 5% CO2 acidification was significantly inhibited by 100 microM 4,4' diisothiocyanatostilbene 2,2' disulfonic acid (DIDS), Cl removal, Na removal and 2 mM amiloride. Prepulsing with 20 mM NH4 in the presence of CO2/HCO3 typically reduced pHi to only about neutral, whereas 50 mM reduced pHi to 6.7-6.8. In the nominal absence of CO2/HCO3, 20 mM NH4 reduced pHi to about 6.7 from which recovery took place at about 58% of the rate seen in different cells in the presence of CO2/HCO3. In the presence of CO2/HCO3, cells prepulsed with 50 mM NH4 had fully recovered to an average pHi of 7.22 +/- 0.04 about 90 min after removal of NH4. However, 90 min after removal of 20 mM NH4 in the absence of CO2/HCO3, average pHi was significantly less (7.05 +/- 0.03). Intrinsic buffering capacity (beta i) was obtained during pulses of CO2, acetic acid or after an NH4 pulse. beta i was significantly reduced in the absence of HCO3, Cl or Na and HCO3. The data provide significant support for an important role of HCO3 in the control of pHi in fast-twitch muscle.

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Section: Discussionmentioning

confidence: 70%

Section: Discussionmentioning

confidence: 86%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Bicarbonate and fast-twitch muscle: Evidence for a major role in pH regulation

1988

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“…More recently Grossie (1985) reported a Ki activity of 119.7 mM, equivalent to a concentration of 157.5 mM with K + microelectrodes in rat skeletal muscle. …”

Section: Mean Arterial Plasma Values Of Ph Pc02mentioning

confidence: 97%

Electrochemical potentials of potassium in skeletal muscle under different metabolic states

Khuri

Agulian

Abdulnour‐Nakhoul

et al. 1992

Journal Cellular Physiology

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Intracellular potassium and membrane potential were measured simultaneously by means of double-barrelled liquid ion-exchange microelectrodes in single fibers of rat thigh muscle in vivo in rats maintained in seven different metabolic states. The K+ equilibrium potential (EK) was more negative than the simultaneously measured membrane potential (Em) in the normal state by 18.4 mV. K+ loading, acute and chronic, resulted in depolarization of Em due to increased serum K+ (hyperkalemia) with no increase in intracellular K+. K+ depletion resulted in hyperpolarization of Em as plasma K+ decreased proportionately more than intracellular K+. Low Na+ diet had no effect. Intracellular K+ was decreased in acute acidosis but not in the chronic state. Thus K+ depletion and acute acidosis are associated with intracellular K+ decrease. The fact that hyperpolarization exists in the former and not the latter is a reflection that hypokalemia accompanies the former condition. The hyperpolarizing states of K+ depletion and chronic acidosis are accompanied by decreased excitability and muscle weakness.

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Mechanosensory encoding in ex vivo muscle–nerve preparations

Housley

Gardolinski

Nardelli

et al. 2023

Experimental Physiology

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New Findings What is the central question of this study? How well have studies using ex vivo muscle‐ nerve preparations represented in vivo features of sensory encoding by low threshold mechanoreceptors in muscle? What is the main finding and its importance? We find experimental adjustments to the ex vivo approach that improve representation of mechanosensory encoding observed in vivo. These adjustments will enhance accuracy in the search for molecular identity and encoding mechanisms of heterogeneous muscle mechanosensory neurons. AbstractOur objective was to evaluate an ex vivo muscle–nerve preparation used to study mechanosensory signalling by low threshold mechanosensory receptors (LTMRs). Specifically, we aimed to assess how well the ex vivo preparation represents in vivo firing behaviours of the three major LTMR subtypes of muscle primary sensory afferents, namely type Ia and II muscle spindle (MS) afferents and type Ib tendon organ afferents. Using published procedures for ex vivo study of LTMRs in mouse hindlimb muscles, we replicated earlier reports on afferent firing in response to conventional stretch paradigms applied to non‐contracting, that is passive, muscle. Relative to in vivo studies, stretch‐evoked firing for confirmed MS afferents in the ex vivo preparation was markedly reduced in firing rate and deficient in encoding dynamic features of muscle stretch. These deficiencies precluded conventional means of discriminating type Ia and II afferents. Muscle afferents, including confirmed Ib afferents were often indistinguishable based on their similar firing responses to the same physiologically relevant stretch paradigms. These observations raise uncertainty about conclusions drawn from earlier ex vivo studies that either attribute findings to specific afferent types or suggest an absence of treatment effects on dynamic firing. However, we found that replacing the recording solution with bicarbonate buffer resulted in afferent firing rates and profiles more like those seen in vivo. Improving representation of the distinctive sensory encoding properties in ex vivo muscle–nerve preparations will promote accuracy in assigning molecular markers and mechanisms to heterogeneous types of muscle mechanosensory neurons.

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Effects of bicarbonate on resting potentials in mammalian skeletal muscle

Cited by 3 publications

References 26 publications

Bicarbonate and fast-twitch muscle: Evidence for a major role in pH regulation

Bicarbonate and fast-twitch muscle: Evidence for a major role in pH regulation

Electrochemical potentials of potassium in skeletal muscle under different metabolic states

Mechanosensory encoding in ex vivo muscle–nerve preparations

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