Magnesium infusion improves endothelium-dependent vasodilation in the human forearm

The effect of intra-arterial magnesium infusion on endothelium-dependent vasodilation (EDV) in the forearm was studied in nine young healthy students (four men and five women). The EDV was assessed as forearm blood flow (FBF), measured by venous occlusion plethysmography, during infusion of methacholine (MCh). Endothelium-independent vasodilation (EIDV) was defined as FBF during infusion of sodium nitroprusside (SNP). During magnesium infusion in the brachial artery, 0.066 mmol/min, the concentration of ionized magnesium in venous plasma in the infused arm increased by 114%, from 0.59 (SD 0.04) to 1.26 (0.34) mmol/L (P = .0002). The FBF at baseline (ie, before administration of MCh or SNP) increased from 3.5 (1.1) to 7.3 (3.4) mL/min/100 mL tissue during magnesium infusion (P = .002). During low-dose MCh administration (2 microg/min), FBF increased by 24%, from 15.4 (5.5) to 19.1 (6.8) mL/min/100 mL tissue (P = .04), and during high-dose MCh administration (4 microg/min) FBF increased by 18%, from 20.3 (6.4) to 24.0 (7.2) mL/min/100 mL tissue (P = .04). The EIDV did not change significantly. Systemic blood pressure was not significantly altered by magnesium infusion. No change in FBF either at rest or during infusion of MCh or SNP was observed during the time-control protocol. In conclusion, this in vivo study showed that intraarterial magnesium infusion increased EDV in the infused human forearm, which is in accordance with findings in previous in vitro and animal experiments.