Figure 2 .
Mechanism of agonist induced contraction showing the release of contracting factors endothelin-1 (ET-1), thromboxane A2, (TxA2 ), and angiotensin II (AII) from the endothelium, as well as the direct stimulation of smooth muscle cell receptors by agonists to increase intracellular calcium ([Ca2+]i ) and induce smooth muscle contraction. Abbreviations: Preproendothelin-1 (Pre-pro ET-1), big endothelin-1 (Big ET-1), arachidonic acid (AA), angiotensin I (AI), angiotensin converting enzyme (ACE), noradrenaline (NA), adrenaline (Ad), phenylephrine (PE), 5-hydroxytryptamine (5-HT), prostaglandins (PG), histamine (Hist), α1 adrenoceptor (α1 ), endothelin receptors (ETA , ETB ), thromboxane receptor (Tx), angiotensin receptor (AT1 ), histamine receptor (H1 ).