New Vasoconstrictor, Bovine Peptide B, released during Blood Coagulation

Abstract

THE final stage of blood coagulation, the conversion of fibrinogen to fibrin by thrombin, is associated with the release of two acidic peptides designated A and B in the bovine system¹. These peptides have been fully characterized by physico-chemical, chemical, and enzyme methods, and the exact ammo-acid sequence has been determined². Laki³ has shown that the peptides released from fibrinogen affect the frog heart, and experiments carried out in this laboratory have shown that bovine peptide B (Fig. 1) in a concentration of 4 × 10⁻⁵ moles/l. produces a slow contraction of the rabbit carotid artery strip, while in a concentration of 1.6 × 10⁻⁶ moles/l. the peptide markedly potentiated the bradykinin-induced contraction of the isolated oestrous rat uterus. The present experiments were undertaken to ascertain whether bovine peptide B had any vasopressor effect in vivo.