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(Circulation Research. 1996;79:909-910.)
© 1996 American Heart Association, Inc.

Articles

Spontaneous Ca²⁺ Oscillations and Waves in Pulmonary Vascular Endothelial Cells

C. William Balke

the Department of Physiology and Department of Medicine, Division of Cardiology, University of Maryland School of Medicine, Baltimore, Md.

Correspondence to C. William Balke, MD, University of Maryland School of Medicine, Department of Physiology, Howard Hall, Room 560, 660 W Redwood St, Baltimore, MD 21201. E-mail bbalke@heart/ab/umd/edu.

Key Words: Ca²⁺ • Ca²⁺ oscillations • Ca²⁺ wave • pulmonary endothelial cell • fura 2

	Introduction

 
Calcium is a ubiquitous second messenger that regulates a number of cellular processes in both excitable and nonexcitable cells.^{1 2 3} Transient elevations in [Ca²⁺]_i (Ca²⁺ transients) are important for the regulation of intracellular processes, and when these Ca²⁺ transients are propagated as Ca²⁺ waves, they may influence or regulate signaling between cells and through tissues. Intracellular and intercellular Ca²⁺ waves have been observed in a variety of cell types and are initiated principally by two types of mechanisms: (1) stimulus-mediated mechanisms (eg, chemical agonist, electrical, or mechanical stimuli) and (2) spontaneously occurring mechanisms. In general, spontaneous Ca²⁺ waves have been observed predominantly in excitable cells¹ (eg, skeletal, cardiac, and vascular smooth muscle cells). Nonexcitable cells, such as endothelial cells, which have been studied principally in isolation or in cell culture preparations, do not show typically spontaneous Ca²⁺ waves, although they do show occasional sporadic Ca²⁺ oscillations.^{4 5 6} Therefore, the prevailing view of Ca²⁺ regulation in pulmonary endothelial cells is that [Ca²⁺]_i is relatively uniform in the absence of chemical agonists or mechanical stimulation. However, the article by Ying et al⁷ in this issue of Circulation Research challenges these rather simple notions of Ca²⁺ homeostasis in pulmonary endothelium and suggests a degree of complexity in Ca²⁺ signaling similar to that found in excitable cells.

The novel findings of these investigators are due, in large part, to their ability to measure intracellular Ca²⁺ transients in individual endothelial cells in an in situ model of endothelial cell function (ie, venular capillaries of the . . . [Full Text of this Article]