The mechanism of Ca2+ release from the SR of permeabilised guinea-pig and rat ureteric smooth muscle

Burdyga, Theodor; Taggart, Michael J.; Crichton, C. A.; Smith, Godfrey L.; Wray, Susan

doi:10.1016/s0167-4889(97)00149-3

Cited by 24 publications

(13 citation statements)

References 15 publications

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“…Thus, in the rat cells the BK channels may be activated by some other mechanism. IP 3 R and release mechanism are present in rat ureteric myocytes, [5,11,13] and activation of BK channels via this route has been suggested in some smooth muscles [4,31]. However, from our data Ca 2+ entry appears to also be necessary for STOC activity.…”

Section: Outward Currentssupporting

confidence: 47%

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Characterisation of the ionic currents in freshly isolated rat ureter smooth muscle cells: evidence for species-dependent currents

Smith

Borisova

Wray

et al. 2002

Pfl�gers Archiv European Journal of Physiology

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To better understand excitability, and hence contraction, the ionic currents underlying the action potential were identified and characterised in enzymatically isolated smooth muscle cells of the rat ureter. Using the whole-cell patch-clamp, under voltage-clamp conditions with K(+) in the pipette, three types of responses occurred to depolarisation: (1) sustained outward current and spontaneous transient outward currents (STOCs); (2) inward current; and (3) fast outward current. Investigation using different voltage protocols and pharmacological blockers and agonists revealed the presence of three outward and two inward currents. The outward currents were: (1) a sustained BK current, sensitive to low concentrations of tetraethylammonium (TEA) and featuring bursts of STOCs superimposed on it; (2) a fast, transient, A-type K current sensitive to 4-aminopyridine; and (3) a TEA and Ca(2+)-insensitive, late K(+) rectifier current. The inward currents were: (1) a fast L-type Ca(2+) channel current sensitive to nifedipine, Cd(2+) and potentiated by Ba(2+); and (2) a Ca(2+)-sensitive Cl(-) channel, which was inhibited by niflumic acid and Ba(2+), and produced a large tail current upon repolarisation at the end of the voltage step. The I- V relationships and peak amplitudes of all the currents are described. The finding of a K(+) rectifier and Ca(2+)-activated Cl(-) channel distinguish the rat ureteric cells from those of the guinea-pig. Thus, as well as the previously established difference in sarcoplasmic reticulum Ca(2+)-release mechanisms, there is also a species difference in ion channel expression in this tissue. We relate these currents to their possible contribution to the characteristically extremely long lasting action potential in the rat ureter.

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Section: Outward Currentssupporting

confidence: 47%

“…sparks, is an activator of BK channels. Rat ureteric cells express few RyR and intact tissue shows little response to ryanodine [5,12,13]. Thus, in the rat cells the BK channels may be activated by some other mechanism.…”

Section: Outward Currentsmentioning

confidence: 99%

Characterisation of the ionic currents in freshly isolated rat ureter smooth muscle cells: evidence for species-dependent currents

Smith

Borisova

Wray

et al. 2002

Pfl�gers Archiv European Journal of Physiology

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“…In rat ureteric myocytes the Ca 2+ waves evoked by photolysis of caged InsP 3 were blocked by InsP 3 receptor inhibitors such as heparin but unaffected by RyR inhibition with ryanodine [50]. Ryanodine blocked the caffeine responses of the guinea pig ureter but not those to carbachol in rat ureter, suggesting that carbachol was releasing Ca 2+ from a ryanodine-insensitive channel [51,52]. In guinea pig intestinal smooth muscle, Ca 2+ oscillations evoked by muscarinic receptor activation were unaffected by Ruthenium Red [53].…”

Section: Interactions Between Ryr and Insp 3 Receptors In The Productmentioning

confidence: 93%

Sarcolemma agonist-induced interactions between InsP3 and ryanodine receptors in Ca2+ oscillations and waves in smooth muscle

McCarron

Bradley

MacMillan

et al. 2003

Biochemical Society Transactions

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Smooth muscle cells respond to InsP(3)-generating (sarcolemma-acting) neurotransmitters and hormones by releasing Ca(2+) from the internal store. However, the release of Ca(2+) does not occur uniformly throughout the cytoplasm but often into a localized area before being transmitted to other regions of the cell in the form of Ca(2+) waves and oscillations to actively spread information within and between cells. Yet, despite their significance, our understanding of the generation of oscillations to waves is incomplete. A major aspect of controversy centres on whether or not Ca(2+) released from the InsP(3) receptor activates RyRs (ryanodine receptors) to generate further release by Ca(2+)-induced Ca(2+) release and propagate waves or whether the entire process arises from InsP(3) receptor activity alone. Under normal physiological conditions the [Ca(2+)] required to activate RyR (approx. 15 microM) exceeds the bulk average [Ca(2+)](c) (cytoplasmic Ca(2+) concentration) generated by InsP(3) receptor activity (<1 microM). Progression of waves and oscillations by RyR activity would require a loss of control of RyR activity and an unrestrained positive feedback on Ca(2+) release. Under store-overload conditions, RyR Ca(2+) sensitivity is increased and this enables waves to be induced by RyR activity. However, the relevance of these Ca(2+)-release events to normal physiological functioning is unclear. The InsP(3) receptor, on the other hand, is activated by Ca(2+) over the physiological range (up to 300 nM) and deactivated by higher [Ca(2+)](c) (>300 nM), features that favour intermittent activity of the receptor as occurs in waves and oscillations. Experimental evidence for the involvement of RyR relies mainly on pharmacological approaches in the intact cell where poor drug specificity could have led to ambiguous results. In this brief review the possible interactions between InsP(3) receptors and RyR in the generation of oscillations and waves will be discussed. Evidence is presented that RyRs are not required for InsP(3)-mediated Ca(2+) transients. Notwithstanding, ryanodine can inhibit InsP(3)-mediated Ca(2+) responses after RyR activity has been induced by caffeine or by steady depolarization which evokes spontaneous transient outward currents (a sarcolemmal manifestation of RyR activity). Ryanodine inhibits InsP(3)-mediated Ca(2+) transients by depleting the store of Ca(2+) rather than by RyR involvement in the InsP(3)-mediated Ca(2+) increase.

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“…26 In many smooth muscles, except the ureter, the pool of Ca 2+ within ryanodine-and IP 3 -sensitive stores appears to be functionally coupled via the colocalization of their receptors within the sarcoplasmic/endoplasmic reticulum membrane. 27,28 A species dependence on the expression of each functioning Ca 2+ store is evident in the SMCs of the ureter, such that only the ryanodinesensitive store appears to be functional in the guinea-pig, 29 whereas only the IP 3 receptor-sensitive Ca 2+ store can be detected in the rat. 29,30 Blockers of phospholipase C (PLC) function and IP 3 formation (neomycin, U73122, xestospongin C) or IP 3 receptors (2-aminoethoxydiphenylborate (2-APB) and heparin) have all been shown to block or reduce electrical oscillations in urogenital 23,31 and gastrointestinal [32][33][34][35] preparations.…”

Section: Role Of Ca 2+ Storesmentioning

confidence: 99%

Spontaneous electrical and Ca²⁺ signals in the mouse renal pelvis that drive pyeloureteric peristalsis

Lang

Hashitani

Tonta

et al. 2010

Clin Exp Pharma Physio

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1. Peristalsis in the smooth muscle cell (SMC) wall of the pyeloureteric system is unique in physiology in that the primary pacemaker resides in a population of atypical SMCs situated near the border of the renal papilla. 2. Atypical SMCs display high-frequency Ca(2+) transients upon the spontaneous release of Ca(2+) from inositol 1,4,5-trisphosphate (IP(3))-dependent stores that trigger cation-selective spontaneous transient depolarizations (STDs). In the presence of nifedipine, these Ca(2+) transients and STDs seldom propagate > 100 mum. Synchronization of STDs in neighbouring atypical SMCs into an electrical signal that can trigger action potential discharge and contraction in the typical SMC layer involves a coupled oscillator mechanism dependent on Ca(2+) entry through L-type voltage-operated Ca(2+) channels. 3. A population of spindle- or stellate-shaped cells, immunopositive for the tyrosine receptor kinase kit, is sparsely distributed throughout the pyeloureteric system. In addition, Ca(2+) transients and action potentials of long duration occurring at low frequencies have been recorded in a population of fusiform cells, which we have termed interstitial cells of Cajal (ICC)-like cells. 4. The electrical and Ca(2+) signals in ICC-like cells are abolished upon blockade of Ca(2+) release from either IP(3)- or ryanodine-dependent Ca(2+) stores. However, the spontaneous Ca(2+) signals in atypical SMCs or ICC-like cells are little affected in W/W(-v) transgenic mice, which have extensive lesions of their intestinal ICC networks. 5. In summary, we have developed a model of pyeloureteric pacemaking in which atypical SMCs are indeed the primary pacemakers, but the function of ICC-like cells has yet to be determined.

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The mechanism of Ca2+ release from the SR of permeabilised guinea-pig and rat ureteric smooth muscle

Cited by 24 publications

References 15 publications

Characterisation of the ionic currents in freshly isolated rat ureter smooth muscle cells: evidence for species-dependent currents

Characterisation of the ionic currents in freshly isolated rat ureter smooth muscle cells: evidence for species-dependent currents

Sarcolemma agonist-induced interactions between InsP3 and ryanodine receptors in Ca2+ oscillations and waves in smooth muscle

Spontaneous electrical and Ca²⁺ signals in the mouse renal pelvis that drive pyeloureteric peristalsis

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The mechanism of Ca2+ release from the SR of permeabilised guinea-pig and rat ureteric smooth muscle

Cited by 24 publications

References 15 publications

Characterisation of the ionic currents in freshly isolated rat ureter smooth muscle cells: evidence for species-dependent currents

Characterisation of the ionic currents in freshly isolated rat ureter smooth muscle cells: evidence for species-dependent currents

Sarcolemma agonist-induced interactions between InsP3 and ryanodine receptors in Ca2+ oscillations and waves in smooth muscle

Spontaneous electrical and Ca2+ signals in the mouse renal pelvis that drive pyeloureteric peristalsis

Contact Info

Product

Resources

About

Spontaneous electrical and Ca²⁺ signals in the mouse renal pelvis that drive pyeloureteric peristalsis