Elemental maps in human allantochorial placental vessels cells: 2. MgCl2 and MgSO4 effects

Extracellular magnesium salts are known to interfere with ionic channels in the cellular membranes. The membrane potential, a regulator of vascular tone, is a function of the physiological activities of ionic channels (particularly, K + and Ca 2+ channels in these cells). These channels regulate the ionic distribution into these cells. Micro‐Particule Induced X‐ray Emission (PIXE) analysis was applied to determine the ionic composition of vascular smooth muscle cells (VSMC) and of vascular endothelial cells (VEC) in the placental human allantochorial vessels in a physiological medium (Hanks‘ solution) modified by the addition of 2 mM MgCl 2 or 2 mM MgSO 4 which block the calcium‐sensitive K + channels (KC a), the ATP‐sensitive K + channels (K ATP) and the voltage‐sensitive K + (K df) and Ca 2+ channels. In VSMC (media layer), the addition of MgCl 2 induced no modification of the K, Cl, P, S and Ca concentrations but increased the Na and Mg concentrations and the addition of MgSO 4 only significantly increased the Mg concentration, the other ion concentrations remaining constant. In endothelium (VEC), MgCl 2 or MgSO 4 addition implicated the same observations as in VSMC. These results confirmed the blockage of K df, KC a, K ATP and Ca channels in VSMC and VEC by magnesium salts, the relationship between Mg 2+ ions and internal Na and demonstrated the possible intervention of a Na +\Mg 2+ exchanger.