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Updated: Aug 14, 2026

Simultaneous Measurements of Intracellular Calcium and Membrane Potential in Freshly Isolated and Intact Mouse Cerebral Endothelium
Published on: January 20, 2019
Calpains: a physiological regulator of the endothelial barrier?
Vera Gonscherowski1, Bernhard F Becker, Louis Moroder
1Department of Physiology, University of Munich, Munich, Germany.
Abstract:
The intracellular protease calpain, abundant in endothelial cells (EC), is assumed to be inactive under physiological conditions but may account for Ca2+ -linked pathophysiological events. However, nonstimulated EC contained autolyzed, activated calpain. Adding 12-48 microM calpain inhibitor I (CI) or 0.5-1 microM of the novel, membrane-permeable conjugate of calpastatin peptide-penetratin (CPP) caused rapid rounding and retraction of cultured EC (phase contrast, capacitance) and translocation of Syk, Rac, and Rho to the membrane, signifying activation upon inhibition of calpain. Isolated hearts (guinea pig) perfused with 12 microM CI or 0.5 muM CPP developed coronary leak. We conclude that calpain is constitutively active in EC and regulates vascular permeability by governing cell-cell attachment.
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