Mg2+-Ca2+ interaction in contractility of vascular smooth muscle: Mg2+ versus organic calcium channel blockers on myogenic tone and agonist-induced responsiveness of blood vessels.
Level 5 - mechanism / opinion, no new human data
Narrative review synthesizing preclinical mechanistic and animal studies
PubMed 3300911 · doi:10.1139/y87-120
What was done
The authors synthesized in vitro and in vivo microscopic and macroscopic vascular smooth muscle studies comparing the vascular actions of magnesium (Mg2+) with organic calcium channel blockers (verapamil, nimodipine, nitrendipine, nisoldipine) across different vascular beds. The review examined effects on myogenic, basal, and agonist-induced vascular tone and calcium transport mechanisms.
What was found
Mg2+ was the only agent evaluated that uniformly inhibited myogenic, basal, and hormone-induced tone in all vascular smooth muscle types examined, acting on voltage-, receptor-, and leak-operated channels. Organic calcium channel blockers demonstrated regional selectivity and heterogeneity across microvascular sites. Mg2+ blocked Ca2+ entry and exit, lowered peripheral and cerebral resistance, relieved vasospasm, and decreased arterial pressure, producing significant vasodilation in intact arterioles and venules at 10–100 µM. The abstract reports that Mg2+ is 3 to 5 orders of magnitude less potent than organic blockers, but it provides no exact numerical variance, p-values, or sample sizes.
Why it matters
This review differentiates the broad, non-selective physiological calcium antagonism of magnesium from the channel-selective profiles of synthetic organic calcium channel blockers. It provides a mechanistic framework for understanding magnesium's generalized vasodilatory actions across regional vascular beds.
Limits
The abstract describes preclinical in vitro and in vivo animal and tissue models rather than clinical human trials. Quantitative effect sizes, comparative variance metrics, and sample sizes are omitted.
Cited by
- supports Excess calcium causes muscle contraction, hypertension, and heart attacks, and magnesium controls calcium and mitigates calcium crystal buildup in damaged heart tissue.