[Studies of kinin-like properties of a new peptide isolated from bovine brain].

Kinin-like properties of two new peptides NRP-11 and P7 which have structural similarity with neurotensin (NT) and kallidin (K) were investigated. It was found that, unlike NT and K, the new peptides possess reduced myotropic and hypotensive activity. On the other hand, similarly to NT and K, the new peptides exhibited a high histamine-releasing activity in rat peritoneal mast cells.

[Cyclic analogs of bradykinin, containing a carboxyl group].

1 alpha-beta-carboxypropionyl-cyclo(9----1 epsilon)-[Lys1, Gly6]bradykinin (Suc-c[Lys1, Gly6]B), 1 alpha-beta-carboxypropionyl-cyclo(10----1 epsilon)kallidin (Suc-cK), cyclo(10 gamma----1 epsilon)-[Glu10]kallidin (c[Glu10]K) and cyclo(11 gamma----1 epsilon)kallidylglutamic acid (cKG) were synthesized. Suc-c[Lys1, Gly6]B and Suc-cK were prepared by acylating the appropriate cyclopeptides with succinic anhydride. c[Glu10]K and cKG were obtained by the classic peptide synthesis, the cyclization being carried out with 61 and 42% yields, respectively.

[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.

[Structural features of linear and cyclic analogs of angiotensin, affecting secretion of histamine from rat mast cells].

Linear and cyclic analogues of angiotensin were studied to clarify the structural properties of peptides possessing a histamine-releasing action. It was shown that an increase in the angiotensin basicity or its cyclization leads to the appearance of the histamine-releasing activity which is not characteristic of the natural hormone. This increase in the basicity of the angiotensin cyclic analogs results in highly active compounds with the EC50 exceeding by 2 to 3 orders of magnitude that of polymyxin B or substance 48/80.

[Cyclic analogs of des-Arg9-[Leu8]bradykinin].

Four cyclic derivatives of des-Arg9[Leu8]bradykinin have been obtained by classical methods of peptide chemistry. They are cyclo-(-X-Arg-Pro-Pro-Gly-Phe-Gly-Pro-Leu-), where X=Lys or none, and cyclo-(Y-Arg-Pro-Pro-Gly-Phe-Ser-Pro-Leu-), where Y= Lys or Orn. Peptide bonds have been formed by the pentafluorophenylester method, and cyclization has been carried out in a diluted dioxane solution with 40% yield.