Incidence des eaux magnésiennes du Sahara Algérien sur la croissance cristalline de l'oxalate de calcium, constituant principal de calculs rénaux

Incidence of magnesium waters from the Algerian Sahara on the crystalline calcium oxalate, main constituent of kidney stones

¹ Laboratoire de Matériaux & Catalyse - Faculté des Sciences - Université Djillali LIABES - Sidi Bel-Abbès (Algérie)
² Laboratoire de Mathématiques - Université Djillali LIABES - Sidi Bel-Abbès (Algérie)
³ Université de Montpellier, 24, quai du Commandant Méric, 34300 Le Grau d'Agde, France

Résumé

Réduire la sursaturation urinaire chez le malade lithiasique par diminution de la précipitation des substances chimiques comme l'oxalate, le calcium, l'acide urique, est un des objectifs visés par l'ingestion d'une quantité importante d'eau de boisson.

Notre étude se propose de tester les eaux de boisson du Sud algérien, riches en magnésium et en calcium. Ces deux éléments sont considérés, respectivement, comme un promoteur et un inhibiteur des calculs rénaux constitués majoritairement d'oxalate de calcium. Quel est leur effet sur le principal constituant chimique du calcul rénal ?

Les teneurs en calcium et magnésium d'une série de 35 échantillons d'eaux de robinet ont été déterminées. Ensuite, l'incidence de ces eaux sur la cinétique de croissance d'une solution sursaturée en oxalate de calcium, par la méthode turbidimétrique in vitro, a été suivie. Les résultats obtenus font apparaître que la majorité des eaux sont magnésiennes (74,28 %).

Le pouvoir inhibiteur de l'eau I % sur la croissance de l'oxalate de calcium n'est pas corrélé au taux de calcium (R_{(1 %, Ca)} = 0,10 p = 0,05). Par ailleurs, le magnésium exerce un effet inhibiteur moyen (R _{1 %, Mg} = 0,62 p = 0,05) sur la croissance cristalline, tandis que le rapport Ca/Mg est corrélé d'une manière importante au pouvoir inhibiteur de l'eau (R_{1 %, Ca/Mg} = - 0,91 p = 0,05).

Abstract

Drinking a significant quantity of water (2 to 3 liters) is the main preventive measure recommended to the lithiasic patient. Its aim is to reduce urinary supersaturation by decreasing the precipitation of the lithogenous substances like oxalate, calcium, uric acid.

Our study proposes to quantify the calcium and magnesium ions contained in drinking water of various areas of South-east and South-west Algeria. These two elements are considered, respectively, like a promoter and an inhibitor of the renal calculi formed mainly of calcium oxalate.

The drinking water supply is ensured by subsoil waters coming from the underground aquifer of Complexe Terminal (CT) and the Continental Intercalate (CI) whose characteristic is to be strongly mineral-bearing.

The analyzed water samples were taken from the tap of consumers. Water concerned comes from towns of South - East and South - West Algeria.

From this point of view, we try to understand the mechanisms of action of drinking water on the dissolution of oxalo-calcic stones. Which is the effect of this water on the main chemical component of the renal stones in Algeria?

The contents in calcium and magnesium of a series of 35 water samples from tap were determined by volumetric technique. Thereafter, we followed the incidence of the drinking water addition, on the kinetics of growth of solution supersaturated out of calcium oxalate, the main constituent of the urinary lithiasis, by the turbidimetric method, in vitro.

The results obtained reveal that the majority of waters are magnesian (74,28%), since the value guides recommended by the World Health Organization is 50 mg/l. 18,41 mg/l ≤ [Mg] ≤ 263 mg/l. Roughly, the half is calcic (51,42 %). The quantity recommended to the lithiasic patient is 150 mg/l. The concentration obtained 64, 16 mg/l ≤ [Ca] ≤ 340, 85 mg/l.

Linear regression lines are traced between the incidence of this water represented by its inhibiting capacity I% and the rate of the magnesium ions at the one hand, between 1% and the rate of calcium on the other hand like between 1% and the report/ratio Ca/Mg. The coefficients of correlation are calculated. This reveals that the inhibiting capacity of water on the growth of calcium oxalate is not correlated in a linear way to the rate of Calcium (1% = 0 02 × Ca + 73,76). The coefficient of correlation R_{(1%, Ca)} = 0,10. Thus, according to these results in vitro, the calcium contained in water does not affect the crystalline growth of oxalate of calcium. In addition, magnesium exerts an average inhibiting effect on the crystalline growth. The equation obtained is the following one: 1% = 0,19 × Mg + 57,60. The coefficient of correlation R_{1%, Mg} = 0,62. On the other hand, the Ca/Mg ratio is linearly correlated in a significant manner with the inhibiting capacity of water 1% = - 15,08 × Ca/Mg + 110,30. The coefficient of correlation R_{1%, Ca/Mg} = - 0,91 p = 0,05.

Indeed, when this ratio decreases, it is the rate of the magnesium which increases at the same time as the incidence rate of this water increases, i.e. water solubilizes oxalate of calcium in the presence of magnesium. This is in fact in conformity with public works on the additional contribution of Mg by oral medication. It is shown that the administration of an additional catch of magnesium prevents the repetition of the oxalocalcic renal calculi. Magnesium seems to be as effective against the stone formation as the diuretic.