Endothelium-dependent hyperpolarizations: the history.

Endothelial cells control the tone and the growth of the underlying vascular smooth muscle by releasing Nitric Oxide (NO). This introduction summarizes the early experiments which first suggested and then demonstrated the existence of an alternative pathway, endothelium-dependent hyperpolarization. It reviews why endothelium-derived hyperpolarizing factor (EDHF) is not likely to be either NO or prostacyclin. It sets the stage for the other contributions of this special issue devoted to EDHF that will discuss in depth the current knowledge concerning endothelium-dependent hyperpolarizations.