Intralymphocyte Free Magnesium in Patients With Primary Aldosteronism

Abstract

Abstract —It is known that hyperaldosteronism has been associated with magnesium deficiency, yet there are no data on the intracellular concentration of ionized magnesium ([Mg ²⁺ _i ]) in subjects with primary aldosteronism (PA). We measured intralymphocyte free magnesium ([Mg ²⁺ _i ]) and intralymphocyte free calcium ([Ca ²⁺ _i ]) in 16 patients with PA and 26 normotensive control subjects (NCs). [Mg ²⁺ _i ] and [Ca ²⁺ _i ] were also measured in blood lymphocytes incubated in vitro with aldosterone, according to a fluorimetric method. In subjects with PA, [Mg ²⁺ _i ] was significantly lower than that in NCs (mean±SD; PA 203±56 μmol/L, NCs 291±43 μmol/L, 95% confidence interval 57 to 119, P =0.001). In the patients, [Ca ²⁺ _i ] did not prove to be statistically different from that of NCs (mean±SD; PA 47.2±10.6 nmol/L, NCs 53.2±11 nmol/L). The lymphocytes exposed to the action of aldosterone showed a significant reduction in [Mg ²⁺ _i ] (n=15, NCs 271±28 μmol/L, aldosterone treatment 188±39 μmol/L, P =0.001, 95% confidence interval 57 to 108). The dose-effect curve of aldosterone on [Mg ²⁺ _i ] showed an EC ₅₀ value of ≈0.5 to 1 nmol/L aldosterone. The reduction in [Mg ²⁺ _i ] mediated by aldosterone is antagonized by the receptor inhibitor of aldosterone; it is inhibited by inhibitors of protein synthesis and is not measurable when the lymphocytes are incubated in an Na ⁺ -free medium. The data are consistent with the hypothesis that aldosterone affects the cellular homeostasis of magnesium, probably through modification of the activity of the Na ⁺ -Mg ²⁺ antiporter.