Cardiovascular effects of fibrinopeptide B

The effect of fibrinopeptide B (FpB) on isolated blood vessels and in the intact rat has been investigated. FpB contracted the rabbit superfused aorta preparation (EC50 = 7.5 nmol) and was some 20 times less potent than noradrenaline. Similarly, FpB (0.2-10 nmol) injected into the rat perfused kidney caused dose related, short-lived increases in perfusion pressure and potentiated the vasoconstrictor effect of injected noradrenaline. These effects were associated with increased efflux of PGE2 (but not TxB2) and were reduced but not abolished by indomethacin (10 microM). FpB injected intravenously into the urethane-anaesthetized rat exhibited vasoconstrictor activity (EC50 = 2.5 micrograms kg-1) but was less potent than noradrenaline (EC50 = 0.9 micrograms kg-1). The doses of FpB required to contract the rabbit isolated aorta and to constrict the vasculature of the rat kidney occur naturally in the bloodstream of patients with thrombotic disease. FpB released at the site of thrombus formation may play a part in regulating local blood vessel calibre.