Magnesium and the calcium paradox: the occurrence of "spasmodic contractions" during Ca2+-Mg2+ -free perfusion of isolated rat heart.
Basic Res Cardiol
; 78(2): 227-38, 1983.
Article
em En
| MEDLINE
| ID: mdl-6307253
ABSTRACT
The effects of omission of Mg2+ during Ca2+-free perfusion (3 min) of either spontaneously beating and electrically stimulated rat hearts were studied. Ca2+-free perfusion per se induced cardiac arrest and coronary vasodilation, and increased intrinsic pulse rate of the heart. Upon reperfusion with Ca2+, cardiac function was lost and parallelled by a sudden and massive release of cellular constituents ("calcium paradox"). Mg2+-free perfusion evoked effects opposite from Ca2+-free, with exception of heart rate which was increased. During Ca2+-Mg2+-free perfusion the electrocardiogram became irregular within 30 s, and this effect was followed by transient "spasmodic contractions". The effects of normal reperfusion were indistinguishable from those observed after Ca2+-free perfusion in the presence of Mg2+. Addition of Mn2+ or La3+ to the Ca2+-Mg2+-free perfusion medium completely inhibited the induction of electrical irregularities and spasmodic contractions. The typical effects of Ca2+-Mg2+-free perfusion are discussed in terms of Mg-Ca and Mg-K interactions at the sarcolemmal surface. It was concluded that our results may contribute indirectly to an explanation of the protective effect of high Mg2+-concentrations during Ca2+-free as well as ischemic perfusion of mammalian hearts.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Cálcio
/
Magnésio
/
Contração Miocárdica
Limite:
Animals
Idioma:
En
Ano de publicação:
1983
Tipo de documento:
Article