The effect of long-term consumption of drinking water with increased magnesium content on renal functions in animals

Introduction. In the literature there are contradictory data on the effect of hardness of drinking water due to high concentration of magnesium and calcium salts on different organs and systems. The aim of the study was to investigate the effect of prolonged consumption of drinking water with increased content of Mg2+ on renal functions in animals. Materials and Methods. Sexually mature Wistar rats of 3 groups during 6 months received drinking water with different content of Mg2+ ions (5 mg/dm3 - control, 35 mg/dm3 - the 1-st group and 70 mg/dm3 - the 2-nd group). To study the renal functions at the 1st, 4th and 6th month the background urine samples within 4 hours and 3 hours after oral intake of 5% of body weight water loads were collected. At the beginning and the end of the experiment, blood was collected to estimate the homeostatic parameters and plasma concentrations of stress hormones (corticosterone, thyrotropin, thyroxine and triiodothyronine). Using the methods of flame photometry, cryoscopy, biochemical and immunoassays the concentrations of electrolytes, osmotically active substances and hormones in urine and plasma were determined. The calculation of urine, osmo-, and ionregulating renal functions was performed by standard formulas. Results. It was shown that prolonged intake of water with increased concentration of Mg2+ caused adaptive changes of osmo- and ionoregulating renal response, characterized by its voltage during the first 4 months, especially in conditions of relative rest and high content of Mg2+ (70 mg/dm3): diuresis reduction, the rise in the relative reabsorption of fluid, the osmolarity of urine and excretion of ions, - so the serum parameters remained within homeostatic level. To the 6th month of experiment the ion-osmotic parameters of plasma and urine in all groups of animals were practically identical. However, it was the decrease of the concentration of stress hormones compared to the control, especially in the 2nd group, which could be due to depletion of hormonal mechanisms responsible for adaptive adjustment of the organism to the drinking water. Conclusions. Long-term consumption of drinking water with high content of Mg2+ causes adaptive adjustment of hormonal and renal responses, the value of which depends on the concentration of ion in the water and the duration of the consumption time.