Effects of Excess K+ on Carbachol-induced Contractions in the Guinea-Pig Tracheal Muscle.

Takemoto, M.; Ito, Yasushi; Takagi, Kenzo; Ogino, Kayo; Tomita, Tadao

doi:10.1540/jsmr.34.45

Cited by 2 publications

(3 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…ASM in general maintains a relatively low intracellular calcium concentration under resting conditions (Jude et al, 2008), thus, providing a reasonable explanation for the major contribution of extracellular Ca 2+ in carbachol-induced contraction in rat trachea. This observation is consistent with a study previously done on guinea-pig trachea (Takemoto et al, 1998), who also reported that carbachol-induced contraction was not affected by thapsigargin.…”

Section: Discussionsupporting

confidence: 93%

Intracellular stored calcium plays a minor role in Gq-coupled receptor-mediated contraction in rat airway smooth muscle

Govindaraju

Lee

Mbaki

et al. 2018

LSMB

View full text Add to dashboard Cite

The general notion of activation of Gq-protein coupled receptors (GPCR) involves the mobilisation of stored and extracellular calcium and leads to smooth muscle tissue contraction. The aim of this study was to investigate the involvement of calcium mediated contractions in vascular and airway smooth muscles. Using standard organ bath procedures, aortic and tracheal rings were obtained from 6 to 8 week-old male Sprague Dawley rats. To activate the Gq protein receptors, phenylephrine (PE), an α1-adrenoceptor agonist, and carbachol, a M3 cholinoceptor agonist was added to baths containing the aortic and tracheal rings, respectively. The maximum response (Emax) to PE was reduced from 158.8 ± 11.8% (n=6) to 62.5 ± 12.4 % (n=8) upon removal of extracellular calcium in Krebs-Ringer solution. Maximal response to PE was also suppressed in the presence of nifedipine, a L-type Ca 2+ channel inhibitor, (70.3 ± 11 %, n=8) and SKF96365, a canonical transient receptor potential cation channel inhibitor, (26.7 ± 13.2 %, n=5) when the influx of extracellular calcium was blocked. Removal of stored calcium also attenuated the PE contraction (p<0.05). Contractile responses to carbachol in the airway were totally abolished in the absence of calcium in the Krebs-Ringer solution (208.6 ± 23 % [n=8] vs 10.7 ± 4.2 % [n=3]). This was different from the aorta where a measurable response was detected despite the absence of external calcium. Blockage of extracellular calcium influx in the presence of nifedipine and SKF96365 also showed similar lack of responses in the trachea. Interestingly, removal of stored calcium did not affect the carbachol responses (p>0.05). From these observations, we conclude that the role of stored and extracellular calcium in Gq protein activation is not the same across different types of smooth muscle tissues.

show abstract

Section: Discussionsupporting

confidence: 93%

Intracellular stored calcium plays a minor role in Gq-coupled receptor-mediated contraction in rat airway smooth muscle

Govindaraju

Lee

Mbaki

et al. 2018

LSMB

View full text Add to dashboard Cite

show abstract

“…15 These Ca 2+ pathways on the cell surface and the endoplasmic membrane contribute to an increase in [Ca 2+ ] i . 16 Because depolarization inhibits ROCC‐mediated Ca 2+ influx in guinea‐pig tracheal muscle, 7 the effects of membrane depolarization to potentiate or attenuate muscle tension generated by an agonist are likely to depend on the balance between Ca 2+ influx through ROCC and Ca 2+ release. In the present study, Ca 2+ ‐induced contractions of the smooth muscle pretreated by PGE 2 were concentration‐dependently potentiated by high K + and TEA in the absence of verapamil and inhibited in its presence, suggesting that VOCC‐mediated Ca 2+ influx should contribute predominantly to the elevation of [Ca 2+ ] i in depolarized cells.…”

Section: Discussionmentioning

confidence: 99%

“… 5,6 However, the mechanisms underlying ROCC inhibition by depolarization are still controversial in guinea‐pig tracheal muscle. 7 The Ca 2+ influx and receptor‐mediated inositol 1,4,5‐triphosphate (IP 3 )‐production trigger Ca 2+ ‐induced Ca 2+ release (CICR) and IP 3 ‐induced Ca 2+ release (IICR) from sarcoplasmic reticulum (SR), respectively, leading to further membrane depolarization, which subsequently causes more VOCC activation. 8 Because of the positive feedback mechanism via VOCC‐mediated Ca 2+ influx, it is hard to observe direct effects of membrane depolarization on Ca 2+ signalling.…”

Section: Introductionmentioning

confidence: 99%

Tonic Potentiation And Attenuation Produced By Membrane Depolarization In Guinea‐Pig Trachealis

Yamaki

Ogawa

Ito

2000

Clin Exp Pharma Physio

Self Cite

View full text Add to dashboard Cite

1. We studied how membrane depolarization directly affected intracellular Ca2+ signalling when voltage-operated Ca2+ channels (VOCC) were not available in guinea-pig tracheal smooth muscle. To block VOCC, we used 3 micromol/L verapamil, which completely abolished high K+ (20-60 mmol/L)-induced contraction, and elevation of fura-2 signal. 2. Muscle tone was generated by adding Ca2+ to the extracellular Ca2+-free solution containing prostaglandin (PG)E2 (100 nmol/L) after abolishing basal tone with indomethacin (1 micromol/L). 3. In the absence of verapamil, high K+ (20-60 mmol/L) solution potentiated 2.4 mmol/l Ca2+-induced sustained contractions. Even in the presence of 3 micromol/L verapamil, replacement with 20 and 40 mmol/L K+ solution induced tonic potentiation, which was changed to attenuation with a higher K+ solution (60 mmol/L), lower extracellular Ca2+ concentration ([Ca2+]o) and pretreatment with cyclopiazonic acid (10 micromol/L), a Ca2+ sequestration inhibitor. 4. These results indicate that the balance between depolarization-dependent Ca2+ release and receptor-operated cation channel inhibition may determine whether tonic potentiation or attenuation is manifested, depending on the availability of VOCC, the magnitude of the depolarization, [Ca2+]o and Ca2+ content in the sarcoplasmic reticulum.

show abstract

Effects of Excess K+ on Carbachol-induced Contractions in the Guinea-Pig Tracheal Muscle.

Abstract: Abstract1. In smooth muscles isolated from the guinea-pig trachea, the effects of dihydropyr idines, nifedipine and nicardipine on contractions produced by carbachol (Cch) were studied in normal (6mM) and excess K+ concentration (60mM

Cited by 2 publications

References 17 publications

Intracellular stored calcium plays a minor role in Gq-coupled receptor-mediated contraction in rat airway smooth muscle

Intracellular stored calcium plays a minor role in Gq-coupled receptor-mediated contraction in rat airway smooth muscle

Tonic Potentiation And Attenuation Produced By Membrane Depolarization In Guinea‐Pig Trachealis

Contact Info

Product

Resources

About