Effects of cerebrovascular challenges on plasma endothelin.

Plasma endothelin elevations have been associated with cerebrovascular pathology. Mechanisms of stimulation, however, are unknown. Therefore, in healthy subjects a marked physiological cerebrovascular response was experimentally provoked by hypercapnia, hypocapnia, and alternating capneic conditions. During these challenges plasma immunoreactive-endothelin-1 (ir-ET-1) concentrations were determined using a radioimmunassay. Physiological effects were continuously recorded for pCO(2), cerebral blood flow velocity, pulse frequency, and arterial blood pressure. No alterations in plasma ET-1 levels were found upon any of the cerebrovascular stimuli. We conclude that massive cerebrovascular challenges in healthy individuals do not lead to high circulating ET-1 levels.