Acute cardiovascular effects of magnesium and their relationship to systemic and myocardial magnesium concentrations after short infusion in awake sheep
Date
2001
Authors
Zheng, D.
Upton, R.
Ludbrook, G.
Martinez, A.
Editors
Advisors
Journal Title
Journal ISSN
Volume Title
Type:
Journal article
Citation
Journal of Pharmacology and Experimental Therapeutics, 2001; 297(3):1176-1183
Statement of Responsibility
Conference Name
Abstract
The temporal relationship between the systemic and myocardial concentrations of magnesium and some of its acute cardiovascular effects were examined after short i.v. infusion administration of magnesium (30 mmol over 2 min) in five awake chronically instrumented sheep. Magnesium decreased mean arterial blood pressure and systemic vascular resistance (SVR) by 23 and 41% from baseline, respectively. These hemodynamic changes were consistent with magnesium producing primary reductions in SVR with partial heart rate (HR)-mediated compensation of blood pressure. Cardiac output and HR increased by 38 and 38% from baseline, respectively. Magnesium had little effect on myocardial contractility, but substantially increased myocardial blood flow (MBF, 77% above baseline) primarily due to direct myocardial vasodilation. The peak arterial and coronary sinus serum magnesium concentrations were 6.94 ± 0.26 (mean ± S.E.M.) and 6.51 ± 0.20 mM, respectively, at 2 min. Both arterial and coronary sinus magnesium concentrations at the end of the study were still more than 3 mM, whereas all the cardiovascular effects were back to baseline. The myocardial kinetics of magnesium was consistent with rapid equilibration of magnesium (half-life 0.4 min) with a small distribution volume (71 ml) consistent with the extracellular space of the heart. In conclusion, magnesium was shown to have a rapid equilibration between the plasma/serum concentrations of magnesium and its extracellular concentration in the myocardium. However, the primary cardiovascular effect of magnesium (reductions in SVR) preceded its extracellular concentrations, and was a direct function of its arterial concentration. A "threshold" model for changes in SVR was preferred when linked to the arterial magnesium concentration.
School/Discipline
Dissertation Note
Provenance
Description
Copyright © 2001 by The American Society for Pharmacology and Experimental Therapeutics