The actions of human atrial natriuretic factor on hepatic arterial and portal vascular beds of the anaesthetized dog

1. The vascular actions of atrial natriuretic factor (ANF) have
been assessed with other vasoactive agents on the hepatic arterial
and portal vascular beds of the anaesthetized dog. 2.
Intra-arterial bolus injections of ANF (0.1-50 nmol) caused graded
increases in hepatic arterial blood flow representing a
vasodilatation of relatively short duration. Vasoconstriction was
never observed. 3. The maximum increase in hepatic arterial blood
was the same for ANF and isoprenaline (Iso) i.e. approximately
60-70% increase over control flow. 4. On a molar basis, ANF was
less potent than Iso although over the higher dose range
(10(-9)-10(-7) mol) its vasodilator activity exceeded that of the
endogenous vasodilator adrenaline. 5. Intraportal bolus injections
(1.0-50 nmol) of ANF did not alter portal inflow resistance since
no changes in portal inflow pressure occurred when the portal
circuit was perfused at constant inflow volume. 6. This
differential action of ANF on the hepatic arterial and portal
vascular beds may provide a change in total liver blood flow in
favour of the arterial component. 7. ANF, by altering hepatic
haemodynamics to favour formation of trans-sinusoidal fluid
exchange, may provide a temporary expansion of the extravascular
fluid reservoir to buffer any increased venous pressure. However,
chronically elevated plasma levels of ANF would encourage the
formation of ascitic fluid.