Structure-activity relationships of the vasopressor activity of canine peptide-A from fibrinogen

Canine peptide-A was demonstrated to be an active vasopressor substance. The effect of intravenous injection of canine peptide-A was a prolonged rhythmic vasoconstriction and is unlike any previously described vasopressor peptides. The intravenous administration of canine peptide-A resulted in a maximum increase in mean blood pressure of 19.0 mm of mercury at a dose level of 2.5-10-minus 2 mumol. This pressor effect exhibited a log proportionality to the injected dose of peptide. The duration of the vasopressor effect was 30 min or greater. A rhythmic variation in pressor response was also observed in all experiments. The canine AP and B peptides were inactive when tested under the same conditions. The relationship between structure and biological activity was investigated. Structural degradation of half of the peptide molecule was performed without loss of vasopressor activity. The canine peptide-A is postulated as assisting in local hemostasis by vasoconstriction.