Portal Pressure Responses to Catecholamines

Summary

The effects of norepinephrine and epinephrine (0.1 and 1.0 μg kg- 1 ) upon portal, arterial, and central venous pressures were measured during drug injections into the portal vein, vena cava, and hepatic artery of anesthetized dogs. The small dose of norepinephrine and epinephrine evoked maximal increases in portal pressure when injected into the portal vein. Except for the responses to portal vein injections, which remained unchanged, these effects were attenuated by splenectomy. The large dose of epinephrine brought about portal pressure increases by all three routes of injection; the maximal change occurred following vena caval injection. These effects were attenuated by splenectomy and by alpha adrenergic blockade. Beta adrenergic blockade potentiated specific portal pressure responses to epinephrine. Norepinephrine elicited the same directional responses as epinephrine but they were lesser in magnitude. The data suggest that portal pressure responses to injected catecholamines are secondary to splenic contraction as well as direct effects on portal venules. The emptying mechanism of the canine spleen appears to be mediated by alpha adrenergic mechanisms.

Technical assistance of Randall W. Barton is gratefully acknowledged.