[1] They are named based on the prostanoid to which they preferentially bind and respond, e.g. the receptor responsive to PGI2 at lower concentrations than any other prostanoid is named the Prostacyclin receptor (IP).
One exception to this rule is the receptor for thromboxane A2 (TP) which binds and responds to PGH2 and TXA2 equally well.
These metabolites contain two double bonds and are named series 2 prostanoids, i.e. PGD2, PGE2, PGF2α, PGI2, TXA2 and PGH2.
), which have one less double bond than the series 2 prostanoids, and they metabolize eicosapentaenoic acid, which has one more double bond than arachidonic acid, to series 3 prostanoids (PGD3, PGE3, etc.
The following table gives these receptors: a) full name; b) shortened names; c) activating prostanoids (presented in order of decreasing potencies);[4] d) time-honored classification as contractile (i.e. contracting smooth muscle), relaxant (i.e. relaxing smooth muscle), or inhibitory (i.e. inhibiting adenyl cyclase (AC) production of cyclic AMP [cAMP]);[5] e) G proteins types to which they link and activate, i.e. those containing the Gs alpha subunit, Gi alpha subunit, Gq alpha subunit and/or G12 subunit;[2][4] and f) signaling pathways which they regulate including Adenyl cyclase which when activated increases cellular cAMP and when inhibited reduces the cellular levels of this secondary messenger; Phosphoinositide 3-kinase which when activated is responsible for forming phosphatidylinositol 3-phosphate, phosphatidylinositol (3,4)-bisphosphate, and phosphatidylinositol (3,4,5)-trisphosphate secondary messengers; Phospholipase C (PLC) which when activated is responsible for forming Inositol trisphosphate (IP3) and diacylglycerol secondary messengers that are, respectively, responsible for raising the levels of Ca2+ in the cellular cytosol to control the activity of Ca2+-cell signaling agents and for activating protein kinase C (PKC) secondary messengers; and Extracellular signal-regulated kinases (ERK), p38 mitogen-activated protein kinases (p38 Mpk), and cAMP response element-binding protein (CREB) which when activated phosphorylate and thereby influence the activity of key proteins that govern cell function.