Prostanoids physiological actions

The PGs, PGI2 and TXA2 collectively exhibit a wide variety of biochemical and pharmacological activities and are iavolved ia both physiological and pathophysiological processes. However, the iadividual compounds show different overall activity profiles sometimes ia opposiag directions. Excellent reviews are available (59—64). A survey of some of the more important biological actions of the prostanoids foUow. 

The identification and characterization of prostanoid receptors has occurred during the past 10 years [11]. These results coupled with studies of PGHS and prostanoid receptor knockout mice have been critical to rationalize earlier results of studies on the physiological and pharmacological actions of prostanoids that had been somewhat confusing and difficult to interpret because PGs were found to cause such a wide variety of seemingly paradoxical effects. 

By 1976, Vane and associates had identified another prostanoid compound, prostacyclin (or PCl2). This compound also arises from PGHj by action of a cytochrome P450-like prostacyclin S3mthase (Fig. 21-7). It is thought to be an important vasoprotective molecule. As with the thromboxanes, prostacyclin undergoes rapid inactivation by hydrolysis to the physiologically inactive 6-0x0-PCF a. 

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