DACTINOMYCIN(R) ANALOGS AS NEUROKININ-2 RECEPTOR ANTAGONISTS

Dactinomycin(R) has recently been shown to be a competitive neurokinin-2 receptor antagonist in addition to its inhibiting action on DNA replication. We investigated in the isolated guinea-pig bronchi the action of 3 Dactinomycin analogues on the contractions evoked by the selective neurokinin-2 receptor agonist [Nle10] neurokinin A(4-10). These analogues included 4,4'-Gly-Dactinomycin and the single peptide lactone of dactinomycin which are inactive on DNA replication and 5,5'-MeLeu-Dactinomycin, which has potent antitumour activity. Independently of their known effect on DNA replication, the three analogues showed neurokinin-2 antagonistic activity which was lower than for Dactinomycin.