ABSTRACT
Seven proctolin analogues (I-VII) modified in position 2 of the peptide chain by Phe (p-guanidino) (I), Phe (p-OEt) (II), Tyr (3'-NH2) (III), Tyr (3'-NO2) (IV), Afb (p-OH) (V) (Afb = 3-amino-4-phenyl-L-butyric acid), Afb (p-NH2) (VI), Afb (p-NO2) (VII), and the tetrapeptide Tyr (3'-NH2)-Leu-Pro-Thr (VIII) were synthesized by the classic liquid-phase method. The biological effects of the peptides were investigated in cardioexcitatory tests on two insect species, the cockroach Periplaneta americana L., and the yellow mealworm, Tenebrio molitor L. Within physiological concentrations (10(-9)-10(-7) M) peptides II, III, and IV stimulated the heart action of P. americana like proctolin itself. Under identical conditions, in the case of T. molitor, only peptide III showed cardiostimulatory properties, whereas other compounds (including II and IV) were inactive at concentrations up to 10(-7) M. Results reported here reflect, with reference to the analogues I-VII, selective recognition of receptors on myocardium of both insect species. The tetrapeptide VIII revealed a weak deacceleratory effect on P. americana and T. molitor heart action.
Subject(s)
Insecta/drug effects , Neuropeptides , Oligopeptides/pharmacology , Peptides/pharmacology , Amino Acid Sequence , Animals , Heart Rate/drug effects , Molecular Sequence Data , Molecular Structure , Oligopeptides/chemical synthesis , Oligopeptides/chemistry , Peptides/chemical synthesis , Peptides/chemistry , Periplaneta/drug effects , Structure-Activity Relationship , Tenebrio/drug effectsABSTRACT
Six proctolin analogues (I-VI) modified in position 1 of the peptide chain by the following amino acids: homo-Arg, Gac, Gav, Gap, Phe (p-guanidino) and Orn, were synthesized by conventional liquid phase method. The myotropic activity of the obtained peptides was investigated in cardioexcitatory test on two insect species, cockroach, Periplaneta americana L., and yellow mealworm, Tenebrio molitor.
