title: Synthetic C3a analogs as specific inhibitors of C3a activity.
abstract: Various C3a-related C-terminal synthetic oligopeptides were investigated for their ability to induce a release of serotonin from guinea pig platelets. The results confirm earlier findings that expression of biological C3a activity requires the four to five C-terminal amino acids of the C3a primary structure and underlines the essential role of the C-terminal arginine. Besides their ability to induce a specific release reaction, these peptides--after short incubation with the platelets--lead to a specific desensitization of the cells for C3a or C3a-related stimuli. Expression of this inhibitory activity required concentrations of the peptides more than 100-fold lower than those that were necessary to induce secretion. The possibility of using C3a analogs as specific inhibitors for C3a offers a valuable tool for in vivo studies of biological C3a activity.
mesh_terms: D000595:Amino Acid Sequence; D000706:Anaphylatoxins / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000818:Animals; D001792:Blood Platelets / Q000187:drug effects; D003176:Complement C3 / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D015926:Complement C3a; D006168:Guinea Pigs; D066298:In Vitro Techniques; D010455:Peptides / Q000494:pharmacology*; D012701:Serotonin / Q000378:metabolism
chemical_list: D000706:Anaphylatoxins; D003176:Complement C3; D010455:Peptides; D012701:Serotonin; D015926:Complement C3a