[General principles of mast cell activation by cyclic analogs of basic vasoactive peptides].

The histamine-releasing activity of some linear and cyclic analogues of bradykinin (BK) and kallidin (K) was studied on rat peritoneal mast cells and compared with that of angiotensin (AT) cycloanalogues assayed earlier. Peptide cyclization, irrespective of the main pharmacological effect of the linear precursors (hypotensive for BK and K, hypertensive for AT), considerably enhanced their histamine-releasing activity. The activity of the tested compounds was found to depend on their amphiphilicity and cycle size. Linear AT and BK and their cycloanalogues bind to different receptor structures on rat mast cells. These findings suggest that BK, K and AT cycloanalogues belong to the same group of nonimmunological mast cell activators whose specific mechanism of action is based on the common structural features resulting from cyclization.