[Changes in balance of ionic currents of cardiac cells as one of the mechanisms of arrhythmia].

Changes in balance of transmembrane ionic currents were achieved in two ways: 1) modifying Na current with lysophosphatidylcholine (LPC), a toxic metabolite of ischemia; 2) modifying Ca current with BAY K 8644, an agonist of Ca channels. Elementary current through Na channel were recorded in an inside-out mode using patch clamp techniques. The effects of BAY K 8644 were studied on the transmembrane potential of guinea pig papillary muscle (PM) and sheep Purkinje fibers (PF).

[Inotropic effect of chlorpromazine on the frog atrium].

The chlorpromazine, a calmodulin inhibitor, has been studied for its action on the contraction force and calcium current of the frog atrium fibres. Chlorpromazine (10(-5) mol/l) was observed to induce maximal increase of the contraction force that 30 min after the agent action amounted to (47.3 + 9.

[Asymmetrical changes in electrical activity of Purkinje fibers and muscle cells after administration of BAY K 8644. A new model of cardiac arrhythmia].

The effects of calcium current agonist BAY K 8644 on transmembrane potential of guinea pig papillary muscle (PM) and sheep Purkinje fibers (PF) were studied. The action potentials (AP) and contractions (C) were recorded. C both of PM and PF increased (two-four times) in response to BAY K 8644 (0.

[influence of Ca channel blockers on the positive inotropic effect of ionophore A23187 in the myocardium].

Calcium ionophore A23187 (10(-5) M) increases the force of contraction of the frog atrium up to 27 + 4.8%. The calcium antagonists d-600 (5 X 10- M), Zn2+ (2 X 10(-5) M), Mn2+ (2 X 10(-4) M) decrease the force of contraction 50, 10 and 20%, respectively, and inhibit the positive inotropic effect of ionophore A23187.

[Relationship between incurrent flow, calcium ion concentration and membrane potential].

A dependence of the inward current across the cell membrane giant neurones at garden snail was investigated under voltage champ. It has been concluded that there are two components of the inward current: a calcium-dependent and I0. The latter current probably was carried by sodium ions.