The synthesis of a biologically active decapeptide having the structure proposed for kallidin II

Actions of some peptides on bronchial muscle

The decapeptide kallidin-10, substance P and angiotensin increased the resistance of guinea-pig lungs to inflation; lysine- or arginine-vasopressin and oxytocin were inactive. Acetylsalicylate antagonized this action of kallidin-10, as it does that of bradykinin, but it failed to antagonize substance P or angiotensin. Bradykinin also increased resistance to inflation of rabbit lungs and, to a lesser extent, rat lungs. It caused a relatively slow contraction of guinea-pig tracheal and bronchial muscle in vitro, but it did not contract isolated rabbit, dog or human bronchus. The relative potencies of different substances on different bronchial test preparations, and also in different species, were not parallel.

Antagonism by mefenamic and flufenamic acids of the bronchoconstrictor action of kinins in the guinea-pig

In the guinea-pig, N-(2,3-xylyl)anthranilic acid (mefenamic acid) and N-(alpha,alpha,alpha-trifluoro-m-tolyl)anthranilic acid (flufenamic acid), two new anti-inflammatory agents, antagonize bronchoconstriction, but not hypotension, produced by kinins. They do not reduce bronchoconstrictor responses to acetylcholine, histamine or 5-hydroxytryptamine. The antibradykinin potencies of mefenamic and flufenamic acids approximately equal that of acetylsalicylic acid when given intravenously and of phenylbutazone when given into the duodenum. After administration of mefenamic and flufenamic acids, the bronchoconstrictor response can be restored by higher doses of bradykinin. The quantitative relationship between the intravenous dose of sodium mefenamate or flufenamate and the dose of bradykinin needed to surmount either antagonist in bronchial muscle fulfils the requirements for competitive antagonism. Antagonism by calcium acetylsalicylate can also be surmounted with higher doses of bradykinin, but in this instance the relationship of antagonist to agonist fulfils requirements for competitive antagonism only at the lower part of the dose range.

NOCICEPTIVE RESPONSES OF GUINEA-PIGS TO INTRADERMAL INJECTIONS OF BRADYKININ AND KALLIDIN-10

Nine behavioural responses were observed to follow with reasonable frequency intradermal injection into guinea-pigs of strongly anisotonic solutions, which are known to cause pain in human skin. These responses were recorded on a form, and a procedure was devised for obtaining a nociceptive score from the records. Intradermal injection of bradykinin or kallidin-10 gave a response pattern indistinguishable from that to a strongly anisotonic solution. Each kinin raised the nociceptive score in response to the control solutions, as also did acetylcholine and histamine; but 5-hydroxytryptamine and pH changes within the range of 3.1 to 10.3 did not significantly raise the control score. The effect of bradykinin was depressed by subcutaneous injection of morphine or codeine, but was unaffected by amidopyrine, calcium acetylsalicylate, chlorpromazine or phenylbutazone.