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Figure 3<br />

Receptor binding curves for the binding of NPC 17410 and NPC 17643 to B2 receptors<br />

from the guinea pig ileum and cloned rat and human B2 receptors. Legends are noted on<br />

the figure.<br />

turn, there appears to be some type of steric interference (or lack of a pocket) that might otherwise<br />

accommodate the ethers of the cis configuration.<br />

Page 126<br />

More recently, bradykinin B2 receptors have been cloned from both rat and human sources [27,28]. In<br />

receptor-binding experiments using these new receptors, selected members of the DHype-containing<br />

decapeptides were used to probe these receptors [24], a representative sample of the data is shown in<br />

Figure 3. Specifically, NPC 17643 (a trans propyl ether of D-4-hydroxyproline at position 7) and NPC<br />

17410 (a cis propyl ether of D-4-hydroxyproline at position 7) were used. Although the trans ethercontaining<br />

decapeptide behaved similarly in binding assays directed toward the bradykinin B2 receptors<br />

in guinea pig, rat, and human, the cis ether-containing decapeptide, NPC 17410, displayed an interesting<br />

pharmacology. In particular, NPC 17410 bound with similar affinity to both the guinea pig and rat<br />

bradykinin B2 receptors, but had an appreciably higher affinity for the human B2 receptor. This result<br />

strongly suggests that there are slight structural differences in the antagonist binding sites of the rat and<br />

human B2 receptors. With clones available for the rat and human bradykinin B2 receptors, this<br />

prompted a systematic search using NPC 17410 binding to rat/human bradykinin B2 receptor chimeras<br />

and point mutations in an attempt to discover residues on the receptor that comprise this antagonist site.<br />

The details and results of the subsequent application of these novel receptor-probing ligands is fully<br />

described later in this chapter.<br />

http://legacy.netlibrary.com/nlreader/nlReader.dll?bookid=12640&filename=Page_126.html [4/5/2004 4:58:51 PM]

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