Prostanoids among

The prostanoid receptors are G-protein coupled rhodopsin-type receptors with seven transmembrane domains [6] (Fig. 3). The overall homology among the receptors is not high, though these receptors conserve the important amino acid sequences in several regions, especially in the seventh transmembrane domain. 

There is a chance therefore to find analogues similar to the IS- or 16,16-alkylated prostanoids of prolonged activity among the heteroprostanoids. 

The level of arterial blood pressure is a function of cardiac output and peripheral vascular resistance which, in turn, are determined by many factors working in an interrelated manner. Prostanoids are included among such factors as many members of this class of arachidonic acid metabolites have a demonstrated capacity to influence the vascular and renal mechanisms of blood pressure control. 

Comparative studies Studies of prostanoids in intermittent claudication have yielded inconsistent results. In a multicenter comparison of three doses of oral iloprost, pentoxifylline, and placebo, conducted in 1998-1999 but published only in 2008, oral iloprost did not improve exercise performance or quality of Ufe pi "]. Serious adverse events did not differ among the groups and neither did any specific cardiovascular events. However, oral iloprost was poorly tolerated and therapy was often interrupted because of headache, flushing, nausea, or diarrhea. 

Another way of looking at the relations among prostanoid receptors is from the standpoint of the signal transduction mechanisms that they engage. Figure 5.8 depicts a phylogenetic tree obtained by comparing the deduced amino acid sequences of the cloned human prostanoid receptors.Such comparison delineates two main receptor subfamilies—one coupled to the stimulation of adenylate cyclase activity (DP, IP, EP2) and another to the increase in intracellular calcium levels (TP, EPi, FP, EP3). 

Prostaglandins (PCs) and prostanoids are well represented among Odocorallia, but seem scarce in Hexacor-allia, in which the only two, 15(S)-PGA2 and 15(S)-PGB2, were found in Palythoa kochii (Zoanthidae). PGA2 inhibits the depolymerization of microtubules in a way similar to... 

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