Effect of the level of magnesium in drinking water on the state of the cardiovascular system of spontaneous hypertensive rats
Authors: Ivanova G. T. , Parastaeva M. M. , Beresneva O. N. 
Published: July 2021

INTRODUCTION. Magnesium is the second most common intracellular cation, is a cofactor for more than 300 enzymes, affects the functional state of the cardiovascular system through various mechanisms, in particular, through the action on the smooth muscle cells of the vessels, modulation of the renin-angiotensin-aldosterone system, regulation of sodium and calcium homeostasis. Therefore, maintaining a normal level of magnesium in the blood is an urgent task, and the consumption of drinking water enriched with magnesium can be considered as a method of correcting an insufficient intake of exogenous magnesium.

THE AIM. The purpose of the study was determined – to evaluate the effect of drinking water with different contents of magnesium ions and a complex of magnesium with calcium on the state of the cardiovascular system of rats with genetically determined arterial hypertension.

MATERIALS AND METHODS. From 6–7 weeks of age, male SHR rats received drinking water of various compositions for two months: in the first group (hCа+Mg) – with increased content of calcium and magnesium (120 mg/l Ca2+ and 45 mg/l Mg2+), the second (nCа+Mg) – drinking water normalized by mineral composition (60 mg/l Ca2+ and 25 mg/l Mg2+), in the third (hMg) – enriched Mg2+ (45 mg/l), the fourth (control) control group – St. Petersburg tap water with a low mineral content (8 mg/l Ca2+ and 3 mg/l Mg2+). WKY rats were divided into 2 groups: one group (hMg) received water enriched with Mg2+ (45 mg/l), the control WKY (control) group received water with a low mineral content (8 mg/l Ca2+ and 3 mg/l Mg2+). After 2 months, the blood pressure of rats on the tail was measured by the cuff method, the level of urea, cholesterol, total calcium, and albumin in the blood serum was analyzed, left ventricular mass index (LVMI) and myocardial mass index (MMI) were calculated. The spontaneous contractile activity of the portal vein (PV) was recorded by myography (in vitro) in isometric mode. The following were analyzed: frequency, total and maximum amplitude of phase-tonic contractions, the area under the contraction curve in 1 min, which characterizes the work performed by the vein. %). 

RESULTS. Enrichment of drinking water with Ca2+ and Mg2+ had a more pronounced antihypertensive effect in SHR rats compared with the hMg2+ group. In WKY rats, magnesium enrichment of water did not affect blood pressure. Modification of the mineral composition of drinking water did not affect MMI and LVMI in both SHR and WKY rats. Interlinear differences were found in the contractile activity of PV in control rats (the amplitude of PV contractions in SHR rats was greater than WKY. Consumption of water enriched with minerals decreased the amplitude of PV contractions, the largest decrease was in the hMg2+ group (in SHR, 2.6 times, in WKY, 1.5 times as compared to the control of the corresponding line). The value of the work performed by the PV in the control SHR rats was greater than in the control rats of the WKY line, and the enrichment of water with magnesium caused a decrease in the work performed by the PV only in rats SHR lines (by 55.6 %), but not for WKY. 

CONCLUSIONS. In rats, the consumption of drinking water enriched only with magnesium has an antihypertensive effect; however, it suppresses the spontaneous contractile activity of PV. It is advisable to use a complex of magnesium with calcium, which lowers blood pressure, but maintains an adequate level of contractile activity of the PV.