Assessment of the effects of endothelin‐1 and magnesium sulphate on regional blood flows in conscious rats, by the coloured microsphere reference technique

Abstract

1 There is evidence to suggest that magnesium (Mg 2+ ) is bene®cial in the treatment of a number of conditions, including pre-eclampsia and acute myocardial infarction. The mode of action of Mg 2+ in these conditions is not clear, although the vasodilator properties of Mg 2+ are well documented both in vitro and in vivo. 2 Previously, we demonstrated that i.v. infusion of magnesium sulphate (MgSO 4 ) alone, or in the presence of vasoconstrictors, caused increases in¯ow and conductance in the common carotid, internal carotid and hindquarters vascular beds, in conscious rats. Therefore, the objective of the present study was to investigate the regional and subregional changes in haemodynamics in response to the vasoconstrictor peptide endothelin-1 (ET-1) and MgSO 4 in more detail, using the coloured microsphere reference technique. 3 Infusion of ET-1 and MgSO 4 had similar e ects on heart rate and mean arterial pressure as in our previous study. Infusion of ET-1 caused a rise in mean arterial pressure and a fall in heart rate, and infusion of MgSO 4 returned mean arterial pressure to control levels with no e ect on heart rate. 4 The responses to MgSO 4 in the presence of ET-1 showed considerable regional heterogeneity with blood¯ow increasing (e.g. skeletal muscle), decreasing (e.g. stomach) or not changing (e.g. kidney). Of particular interest was the ®nding that MgSO 4 caused increases in¯ow in the cerebral and coronary vascular beds. 5 This, and our previous studies, have shown that MgSO 4 can reverse vasoconstriction in a number of vascular beds, and indicate that this compound may have therapeutic bene®t in conditions associated with vasospasm.

Magnesium sulfate therapy of preeclampsia: an old tool with new mechanism of action and prospect in management and prophylaxis

“…Magnesium has in vivo and in vitro vasodilator properties, and MgSO 4 injection has been reported to reduce total peripheral resistance and counteract the vasospasm induced by vasoconstrictor substances, such as endothelin-1, in several vascular beds. 32 This result could explain the preserved normal histological structure and the amelioration of hypertension in the PRE þ MgSO 4 group in the current study. Similarly, MgSO 4 was able to relieve coronary Table 3 Morphometric criteria of pups in the CON-P, preeclampsia (PRE) and PRE þ MgSO 4 groups of rats at day 21 of pregnancy vasospasms, increase blood flow and improve endothelial function, leading to a good response in several ischemic cardiac problems.…”

Initial Clinical Experience of Vasodilatory Effect of Intra-cisternal Infusion of Magnesium Sulfate for the Treatment of Cerebral Vasospasm After Aneurysmal Subarachnoid Hemorrhage

“…25) Mg 2＋ also attenuates the effects on the cerebral arteries of endothelin-1 and oxyhemoglobin, which are considered to be important potent vasoconstrictors after SAH. 7,11) The present study demonstrated that intra-cisternal infusion of magnesium sulfate solution has a vasodilatory effect on the spastic cerebral arteries of patients with symptomatic vasospasm following aneurysmal SAH. The effect of magnesium infusion was most prominent in the arteries near to the cisternal drainage placement because the repeated angiography was performed shortly after the start of infusion (3 hours).…”

Incidence, hemodynamic, and electrical characteristics of spreading depolarization in a swine model are affected by local but not by intravenous application of magnesium

“…In addition, Mg 2þ can inhibit flux through voltagedependent Ca 2þ channels in vascular smooth muscle cells, 3 and could thereby limit inappropriate vasoconstrictor responses in the wake of SD in injured tissues. Prior work has shown that intracisternal Mg 2þ reduces the frequency and the depolarization time of SD and it reduces lesion volume following subarachnoid hemorrhage in rats.…”