Corticosteroids and vascular tone: mapping the messenger maze.

The effects of corticosteroids on vascular tone have been recognized since the 1940s. However, despite repeated demonstration of pharmacological effects both in vitro and in vivo, their physiological significance as regulators of tone in health remains to be established. Evidence that abnormal vascular reactivity is important when adrenal steroid production is deranged is more convincing, and probably contributes to the changes in blood pressure seen in conditions of corticosteroid excess and deficiency. It remains speculative whether the same mechanisms contribute to the pathogenesis of other hypertensive syndromes and of circulatory shock. Recently, the effects of corticosteroids have been studied in cultured vascular cells. These studies exploit our improving understanding of the actions of steroid hormones on their target cells and better appreciation of the diversity of biochemical signals in the vessel wall which mediate the response to vasoactive stimuli. They include measurements of endothelium-derived factors (which act on neighbouring vascular smooth muscle cells), contractile cell-surface receptors and intracellular second messengers (released within the contractile cell in response to the activation of surface receptors). Such studies have shown a number of interactions between corticosteroids and newly discovered biochemical messengers. In this review we assess whether our interpretation of the older evidence that steroids affect vascular tone is influenced by recent studies of their cellular effects, and whether we can now deduce the role of corticosteroids in vascular physiology and pathology.