Bradykinin analogs containing beta-homoamino acids

Area of Science:

• Biochemistry
• Pharmacology

Background:

• Bradykinin is a peptide hormone with significant physiological roles, including vasodilation.
• Understanding bradykinin's metabolism and developing stable analogs is crucial for therapeutic applications.

Purpose of the Study:

• To synthesize and characterize novel bradykinin analogs, specifically [8-beta-homophenylalanine]bradykinin and [7-beta-homoproline]bradykinin.
• To evaluate the vasodepressor activity and metabolic stability of these analogs in vivo and in vitro.

Main Methods:

• Solid-phase synthesis was employed to create the two new bradykinin analogs.
• Vasodepressor activity was assessed in anesthetized rats.
• In vitro degradation by rabbit lung dipeptidylcarboxypeptidase was evaluated.
• In vivo resistance to degradation was inferred by the effect of SQ 20881 (BPP9a), a dipeptidylcarboxypeptidase inhibitor.

Main Results:

• [7-beta-homoproline]bradykinin exhibited equipotent vasodepressor activity compared to native bradykinin in rats.
• [8-beta-homophenylalanine]bradykinin was significantly less potent (30-100 times) in its vasodepressor effect.
• Both analogs showed resistance to in vitro degradation by dipeptidylcarboxypeptidase.
• Only [7-beta-homoproline]bradykinin appeared resistant to in vivo degradation, as its hypotensive effect was not enhanced by SQ 20881.

Conclusions:

• The [7-beta-homoproline]bradykinin analog is a potent and metabolically stable bradykinin analog.
• The [8-beta-homophenylalanine]bradykinin analog is less potent and susceptible to in vivo degradation.
• These findings highlight the potential of specific modifications in bradykinin structure for developing pharmacologically improved agents.