Abstract
It was investigated whether the negative inotropic effect of magnesium in mammalian heart ventricular muscle is due to inhibition of the calcium inward current. Whole-cell voltage-clamp experiments were carried out with isolated guinea-pig heart cells. The sodium inward current was inactivated by a conditioning pre-pulse or by addition of tetrodotoxin. Magnesium concentration dependently and reversibly diminished the calcium inward current (by about 45% after an increase in magnesium concentration, from 1.2 to 9.6 mM). The decrease was mainly due to diminution of the maximally available calcium inward current but was additionally due to a shift of the current-voltage relationship to more positive potentials. The crucial dependence of the inhibition of the inward current on the pre-pulse potential was demonstrated. Conditioning dennlarization to potentials more negative than -40 mV led to an increase of an inward current by magnesium. This was probably the consequence of incomplete inactivation of the sodium current and the shift of its current-voltage relationship by the divalent cation.
| Original language | English |
|---|---|
| Pages (from-to) | 243-248 |
| Number of pages | 6 |
| Journal | European Journal of Pharmacology |
| Volume | 204 |
| Issue number | 3 |
| DOIs | |
| State | Published - 12 Nov 1991 |
Keywords
- Ca inward current
- Ca-Mg antagonism
- Heart ventricular muscle