[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.

[Effects of diltiazem and tetrodotoxin on the development of hypoxic contracture of the guinea pig myocardium].

In the isolated electrically stimulated right ventricular papillary muscles the onset of hypoxic contracture occurred 7 +/- 1.2 min and reached maximum 29.2 +/- 4.

[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.