Abstract There exists a considerable gap between the recognition of the effects of pressor hormones and the understanding of their mechanisms. Studies are necessary to provide a more accurate basis for potential therapeutic interventions on the hormonal mechanisms of hyper- and hypotensive states. From recent and previous experimental results, a modified model of vascular smooth muscle cell activation is emerging. In this model, contraction is a complex process involving Ca 2+ release, protein kinase C and ionic channel activation and modification in pH and energy metabolism. The combined action of these processes is necessary for the full expression of the contractile response.