THE haemodynamic and respiratory responses caused by i.v. administrati
on of endothelin-1 (ET-1) (20-100 pmol/kg) were studied in anaesthetiz
ed spontaneously breathing pigs. Intravenous bolus administration of s
ynthetic ET-1 (40-100 pmol/kg) caused a transient decrease followed by
a long-lasting increase in mean pulmonary arterial pressure and dose
dependent vasoconstriction both in the systemic and pulmonary circulat
ions. The effect on pulmonary arterial pressure was biphasic, with an
initial transient fall followed by a long-lasting dose dependent incre
ase. A biphasic response of the systemic mean arterial pressure was de
monstrated only at a high dose of ET-1 (100 pmol/kg). ET-1 administrat
ion did not significantly change breathing pattern or phasic vagal inp
ut, but caused a significant decrease in passive compliance. Passive r
esistances or active compliance and resistances of the respiratory sys
tem were not modified. These results suggest that in the pig ET-1 is a
more potent constrictor of vascular than of bronchial smooth muscle.
The vasoconstrictor activity was greater in the pulmonary than the sys
temic circulations.