Canadian journal of physiology and pharmacology
-
Can. J. Physiol. Pharmacol. · May 1990
Role of beta-adrenergic agonists in the control of vascular capacitance.
The role of beta-adrenergic agonists, such as isoproterenol, on vascular capacitance is unclear. Some investigators have suggested that isoproterenol causes a net transfer of blood to the chest from the splanchnic bed. We tested this hypothesis in dogs by measuring liver thickness, cardiac output, cardiopulmonary blood volume, mean circulatory filling pressure, portal venous, central venous, pulmonary arterial, and systemic arterial pressures while infusing norepinephrine (2.6 micrograms.min-1.kg-1), or isoproterenol (2.0 micrograms.min-1.kg-1), or histamine (4 micrograms.min-1.kg-1), or a combination of histamine and isoproterenol. ⋯ Histamine caused a marked increase in portal pressure and liver thickness and decreased cardiac output, but it had little effect on the estimated mean circulatory filling pressure. Isoproterenol during histamine infusions reduced histamine-induced portal hypertension, reduced liver size, and increased cardiac output. We conclude that the beta-adrenergic agonist, isoproterenol, has little influence on vascular capacitance or liver volume of dogs, unless the hepatic outflow resistance is elevated by agents such as histamine.