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  • 1
    Electronic Resource
    Electronic Resource
    Contractile response and electrophysiological properties in enzymatically dispersed smooth muscle cells of rat vas deferens (1987)
    Springer
    Pflügers Archiv 408 (1987), S. 112-119 
    Details
    ISSN: 1432-2013
    Keywords: Rat vas deferens ; Single smooth muscle cells ; Sensitivity to norepinephrine ; Voltage clamp ; Action potentials ; Membrane currents ; Ca current
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Electrophysiological studies were performed on single smooth muscle cells isolated from the vas deferens of the rat. The tissue was preincubated in Ca-free modified Tyrode's solution for 1 h and then transferred to a high-K solution for 1 h. It was next minced and treated with the enzyme solution composed of 600–800 unit/ml collagenase and 40 unit/ml elastase. The procedure yielded about 50% spindle shaped Ca-tolerant cells (100–250 μm in length and about 10 μm in diameter). These cells could contract during the superfusion with the solutions containing 10−8 to 10−3M norepinephrine (NE) or adenosine triphosphate (ATP). The cells isolated from the epididymal portion were more sensitive to norepinephrine than were those from the prostatic part. Their basic electrical properties were studied using tight-seal suction electrode technique. The cells had resting potentials around −40 mV and their input resistance was about 0.8 GΩ. Action potentials could be evoked by application of depolarizing current. During whole cell voltage clamp, an inward current followed by an outward current was recorded when 800 ms pulses from a holding potential of −60 mV to test potentials positive than −40 mV were applied. The transient outward current generally recorded in other smooth muscle cells was not seen in these cells. The amplitude of the inward current was Ca dependent and sensitive to a Ca antagonist, nicardipine, indicating that Ca ion is the main carrier of this component of the current. When the pipette was filled with Cs-containing solution, the outward current was abolished. In this condition, the reversal potential of Ca current was +53.4 mV, and the time course of inactivation was composed of more than one exponential component. The results suggest that these isolated cells retain many characteristics of analogous multicellular preparation and that they are a useful model of the postsynaptic properties in smooth muscle especially when studied electro-physiologically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00581338
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Fast and slowly inactivating components of Ca-channel current and their sensitivities to nicardipine in isolated smooth muscle cells from rat vas deferens (1988)
    Springer
    Pflügers Archiv 411 (1988), S. 289-295 
    Details
    ISSN: 1432-2013
    Keywords: Vas deferens ; Isolated smooth muscle cells ; Whole cell recording ; Ca-channel current ; Inactivation ; Sensitivity to nicardipine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract (1) Fast and slowly inactivating components of Ca-channel current were compared to clarify whether more than one type of Ca-channel exists in smooth muscle cells from rat vas deferens using the whole cell variant of the patch clamp technique. The pipette was filled with 150 mM Cs solution to eliminate outward current and Ba was used as the charge carrier for Ca-channel current. (2) When activated by a 5 s test pulse to 0 mV from a holding potential of −60 mV, the inactivation process of Ba-current was well fitted by the sum of two exponentials. The time constant of the faster inactivating component was 100–300 ms and that of the slower inactivating component was 1.5–3 s. Steadystate inactivation curves of the fast- and slow-components were very similar. (3) The inward current activated at 0 mV from −80 mV was inactivated faster than that from −30 mV. The voltage-dependencies of the peak current from holding potentials of −30 mV and −80 mV were similar. Both had voltage threshold at −30 mV and were maximal at +10 mV. (4) Low concentrations of nicardipine (10−9 to 10−7 M) preferentially inhibited the slow component while higher concentration (10−6 to 10−5 M) were required to block the fast component. The current activated from a holding potential of −30 mV was almost fully suppressed by 10−7 M nicardipine whereas that from −80 mV was blocked only slightly. The voltage dependencies of the peak currents before and during the superfusion with nicardipine (10−7 M) were similar although the peak amplitude was suppressed in the presence of the drug. (5) These results suggest that the existence of either (a) two populations of Ca channels that differ in the time course of inactivation and the sensitivity to nicardipine, but have nearly identical dependence on membrane potential or (b) one population of Ca channel having two different states of inactivation and the sensitivity of nicardipine, in rat vas deferens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00585117
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Adenosine triphosphate-activated inward current in isolated smooth muscle cells from rat vas deferens (1987)
    Springer
    Pflügers Archiv 409 (1987), S. 644-646 
    Details
    ISSN: 1432-2013
    Keywords: Smooth muscle cells ; ATP-activated channel ; purinergic neurotransmission
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The electrophysiological effect of adenosine triphosphate (ATP) on the enzymatically dispersed smooth muscle cells from rat vas deferens was investigated. ATP always induced depolarization accompanied with a reduction in membrane resistance. In a whole cell voltage clamp experiment, an inward current was recorded when the cell was exposed to ATP-containing solution. The ATP-induced current disappeared within 2min even in the continuous presence of ATP, which may indicate that the cells were desensitized to this compound. The ATP-induced current was also recorded in the cells superfused with 10−5M nicardipine or in the Cs-loaded cells, eliminating the possible involvement of voltage-gated Ca and K current. During cell-attached patch clamp, an elementary current having a mean conductance of 20pS was observed when the intrapipette solution was changed to ATP-containing solution. The estimated zero current potentials of the ATP-activated macroscopic current and elementary current were about 0mV. These results suggest that ATP exerts its transmitter-like action by activating ion channels in smooth muscles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584668
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Involvement of calcium in calcium-current inactivation in smooth muscle cells from rat vas deferens (1987)
    Springer
    The journal of membrane biology 100 (1987), S. 13-19 
    Details
    ISSN: 1432-1424
    Keywords: smooth muscle cells ; Ca channel ; whole cell recording ; inactivation ; Ca dependency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Ca-channel currents were recorded in Cs-loaded single smooth muscle cells from rat vas deferens to define the dependence of the inactivation time course on Ca concentration. The decay of Ca-channel current obtained in a Ba2+- or Sr2+-containing external solution during long voltage-clamp pulses was much slower than that in a Ca-containing solution. The difference was not due to a change in the surface potential of the membrane as judged from the steady-state activation and inactivation curves. When Ca was the charge carrier, increasing external Ca concentration slightly accelerated the rate of inactivation. In addition, the rate of inactivation of Ca-channel current in 10.8mm Ba was also accelerated by adding Ca to the external solution in a concentration-dependent manner. The time course of Ca-current inactivation was slowed when the cells were dialyzed with a high concentration of citrate, a Ca-chelating agent. From these results, we concluded that a mechanism regulated by intracellular Ca activity plays a role in the inactivation of Ca channels in smooth muscle. The Ca-dependent process may protect against Ca overload by regulating Ca entry in smooth muscle cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02209136
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    Paper (German National Licenses)
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