CARDIOVASCULAR ACTIONS OF DOGFISH UROTENSIN-II IN THE DOGFISH SCYLIORHINUS-CANICULA

Bolus injections of synthetic dogfish urotensin II (0.1-1.0 nmol) into the celiac artery of the conscious dogfish Scyliorhinus canicula (n = 8) resulted in sustained and dose-dependent increases in arterial blo od pressure and pulse pressure. A maximum rise in mean arterial pressu re of 10.5 +/- 1.2 mmHg (equivalent to 38.6 +/- 4.2% over mean basal v alues) and a maximum increase in pulse pressure of 3.9 +/- 0.8 mmHg wa s elicited by injection of 0.5 nmol of peptide. In comparison, a bolus injection of epinephrine (5 nmol) elicited a rise of 24.8 +/- 3.3% in mean arterial pressure. Bolus injection of 0.5 nmol synthetic goby (G illichthys mirabilis) urotensin II under the same conditions did not e licit a significant hypertensive response. When dogfish urotensin II ( 0.5 nmol) was administered 3 min after an intra-arterial injection of phentolamine, the rise in arterial blood pressure was completely aboli shed. Dogfish urotensin II produced a dose-dependent contraction (pD2 = 6.58 +/- 0.07; n = 8) of isolated rings of vascular muscle prepared from the first afferent branchial artery of the dogfish. A maximum con tractile force of 1.3 mN was produced by 10(-5) M peptide. The urotens in II-induced contraction of the vascular rings was unaffected by pret reatment with tetrodotoxin (1 muM) or indomethacin (14 muM). It is con cluded that urotensin II has potent hypertensive activity in the dogfi sh that is mediated, at least in part, through release of catecholamin es, but the sustained nature of the pressor response suggests that the peptide may have a direct action on the heart.