Referenced in: none

Automatically associated channels: Kv2.1

Title: Magnesium and the calcium paradox: the occurrence of "spasmodic contractions" during Ca2+-Mg2+ -free perfusion of isolated rat heart.

Authors: J M Koomen, J A Schevers, J Noordhoek, A N Zimmerman

Journal, date & volume: Basic Res. Cardiol., 1983 Mar-Apr , 78, 227-38

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/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.