Related Experiment Videos
Post-ischemic contractile dysfunction does not correlate with an elevated intracellular free [Mg2+]: a 31P-NMR study
J H Schreur1, R de Beer, C J Van Echteld
1Interuniversity Cardiology Institute of The Netherlands, Department of Cardiology, University Hospital, Utrecht.
Abstract:
The aim of this study was to investigate whether intracellular free Mg2+ (Mgr), which increases during myocardial ischemia due to hydrolysis of ATP, remained elevated during reperfusion after a relatively short period of ischemia and thereby could account for temporary post-ischemic contractile dysfunction, often referred to as stunning. 31P-magnetic resonance (31P-NMR) spectroscopy was used to follow creatine phosphate, adenosine triphosphate, intracellular inorganic phosphate, intracellular pH and Mgr simultaneously with left ventricular developed pressure (LVDP) and coronary flow in isolated rat and rabbit hearts, which were perfused (37 degrees C) according to Langndorff. LVDP was measured in an isovolumic way by means of an intraventricular latex balloon. Rat hearts (300 beats/min) were made globally ischemic for 15 min and rabbit hearts (180 beats/min) for 15 or 20 min. All hearts were reperfused for 60 min. Control hearts were perfused for 75 min without being made ischemic. During ischemia Mgr (mmol/l) increased from 0.76 +/- 0.20 to 4.34 +2- 1.99 in the rat hearts, and from 0.72 +/- 0.22 to 2.18 +/- 1.06 (15 min) and 2.35 +/- 1.26 (20 min) in the rabbit hearts. During reperfusion Mgr in the three groups returned to the level of the control hearts within 7.5 min, and LVDP within 25 min. At the end of the reperfusion period ATP content amounted to 56 +/- 17% (rat hearts), 66 +/- 10% (rabbit hearts; 15 min ischemia group) and 61 +/- 7% (rabbit hearts; 20 min ischemia group) of the pre-ischemic levels. The results confirm that in vitro stunning is a short-lived phenomenon and indicate that an increased Mgr is not involved in this temporary mechanical dysfunction.
Insights
Elevated intracellular free magnesium (Mgr) during reperfusion does not cause temporary stunning after short myocardial ischemia. Studies show Mgr levels normalize quickly, indicating other factors are responsible for stunning.
Area of Science:
- Cardiology
- Biochemistry
- Physiology
Background:
- Myocardial ischemia leads to ATP hydrolysis, increasing intracellular free Mg2+ (Mgr).
- Post-ischemic stunning is a temporary contractile dysfunction following ischemia and reperfusion.
- The role of elevated Mgr in stunning remains unclear.
Purpose of the Study:
- To investigate if elevated intracellular free Mg2+ (Mgr) during reperfusion contributes to temporary post-ischemic contractile dysfunction (stunning).
Main Methods:
- Utilized 31P-magnetic resonance (31P-NMR) spectroscopy in isolated rat and rabbit hearts.
- Monitored creatine phosphate, ATP, inorganic phosphate, intracellular pH, and Mgr.
- Measured left ventricular developed pressure (LVDP) and coronary flow during global ischemia and reperfusion.
Main Results:
- During ischemia, Mgr significantly increased in both rat and rabbit hearts.
- Mgr levels returned to baseline within 7.5 minutes of reperfusion.
- Left ventricular developed pressure (LVDP) recovered within 25 minutes, and ATP levels partially recovered.
Conclusions:
- In vitro stunning is a transient phenomenon.
- Elevated intracellular free Mg2+ (Mgr) is not implicated in temporary post-ischemic contractile dysfunction.
- Other mechanisms likely underlie myocardial stunning.