Transmembrane Currents in Capillary Endothelial Cells are Modulated by External Mg²⁺ Ions

Abstract

The capillary endothelium of the brain is involved essentially in the preservation of the blood-brain barrier and in the regulation of brain microcirculation. As a biological membrane lining the inner wall of blood vessels, the endothelium is exposed to many environmental alterations of the blood composition. In this context, it is known that changes in the concentration of extracellular magnesium ions ([Mg²⁺]_o) play important roles in the control of vascular reactivity, by modulating the myogenic tone and the contractile response of vascular smooth muscle cells to various physiological and pharmacological stimuli (Altura & Altura, 1981). Recent studies on endothelial cells demonstrate that changes in [Mg²⁺]_o can modify the state of the cytosolic free calcium (Zhang et al, 1993). The aim of the present study was, therefore, to investigate whether in fact this modulatory effect of Mg²⁺ could be ascribed to some effect on the excitability of the cell membrane of endothelial cells. For this purpose, transmembrane currents of rat brain capillary endothelial cells (BCECs) were investigated in whole-cell experiments with the patch-clamp technique (Hamill et al, 1981).