Myocytes isolated from porcine coronary arteries: reduction of currents through L-type Ca-channels by verapamil-type Ca-antagonists

• Autorzy: Klockner U. , Isenberg G.
• Języki publikacji: EN

Abstrakty

EN

Myocytes were enzymatically isolated from large epicardial arteries of the pig. In the cell attached configuration, we studied currents through L-type Ca-channels. At 22°C, open channel conductance was 9 pS with 110 mM Ba²⁺ and 24 pS with 110 mM Ba²⁺ as charge carrier. According to the life time of the open state, 2 ’modes’ of gating are distinguished; mode 1 contributed time constants shorter than 1 ms, mode 2 those longer than 6 ms to the open time distribution. Mode 2 openings appeared spontaneously, more frequently with Ba²⁺ than with Ca²⁺ as charge carrier. The Ca-agonist Bay K 8644 (0.5 pM) facilitated the appearance of mode 2. Bath application of the phenylalkylamine D600 (1 µM) did not change the gating modes, but it reduced the channel openness by increasing the percentage of blank records. With whole cell recordings, we studied reduction of Ica by 1 µM D 600 at 3.6 mM [Ca²⁺] and 35°C. At a holding potential of -45 mV, D600 induced an ’initial block’ of 35% (10% at -65 mV). Upon repetitive 1 Hz pulsing (170 ms to 0 mV) an additional, ’use-dependent’ block developed with time. More negative holding potentials attenuated reduction of Ica by D600, hyperpolarizations to -100 mV had an ’unblocking’ effect. In regard to reduction of Ica, we compared the partially uncharged D 600 (membrane permeable) with the completely charged compound D890 (membrane impermeable). When applied with the bath, 1 or 10 pM D 600 reduced Ica dose-dependently whereas D 890 was ineffective. When D890 was applied via the patch electrode to the cytosol, it reduced Ica. We discuss that D 600 enters the cell in the uncharged lipid soluble form and reaches form the inside its receptor associated with the Ca-channel.

Słowa kluczowe

EN

calcium channel; calcium antagonist; vascular smooth muscle cell; myocyte; L-type calcium channel; coronary artery; verapamil

• Wydawca: -
• Czasopismo: Journal of Physiology and Pharmacology
• Rocznik: 1991
• Tom: 42
• Numer: 2
• Opis fizyczny: p.163-179,fig.,ref.

Twórcy

autor

Klockner U.

• Department of Physiology, University of Cologne, Robert-Koch-Str. 39, 5000 Koln, 41, Germany

autor

Isenberg G.

• Department of Physiology, University of Cologne, Robert-Koch-Str. 39, 5000 Koln, 41, Germany

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