Plasma and lymph dopamine-beta-hydroxylase and norepinephrine during carotid occlusion.

Dopamine-beta-hydroxylase (DBH) and norepinephrine (NE) levels in superior mesenteric venous (SMV) and arterial blood and in intestinal lymph were determined sequentially before and during carotid artery occlusion (CAO) in anesthetized rabbits. During the first 15 min of CAO, SMV plasma NE increased 77% but SMV plasma DBH increased only 11%. During the second 15 min of CAO, SMV NE declined to 36% above control but SMV DBH rose further and peaked to 29% above control after CAO was released; arterial DBH and NE showed small insignificant changes. Lymph DBH and NE increased simultaneously throughout the period of CAO. Increases in mean arterial pressure during CAO correlated with superior mesenteric venous NE (r = 0.58, P less than 0.01). In additional experiments, hepatic vein plasma NE was 74% lower than portal vein NE. Thus, during acute sympathetic activation, DBH and NE increase in mesenteric venous plasma and intestinal lymph but the peak response of plasma DBH lags behind that of NE. The degree of NE change in the general circulation is minimized due to hepatic clearance of NE.