Histamine-induced fluid efflux in the canine forelimb as affected by carotid occlusion or hemorrhage.

Infusion of catecholamines concurrently with histamine into the forelimb of the dog prevents histamine-induced increases in lymph flow, protein concentration and forelimb weight. This study tested whether the sympathoadrenal discharge of catecholamines induced by carotid occlusion or hemorrhage would similarly prevent histamine's actions in the canine forelimb. Carotid occlusion or hemorrhage, begun after 30 minutes of histamine infusion (4 micrograms base/min), resulted in a reduction in lymph flow but lymph protein concentration was not changed. Infusion of histamine into the forelimb for 30 minutes in control studies caused the forelimb to gain weight. In experimental studies hemorrhage, begun at one minute after the start of histamine significantly reduced this weight gain but occlusion of the carotid arteries at one minute after the start of histamine did not significantly affect weight gain. These results show that sympathetic nerve activity can lower elevated lymph flow and that sympathetic activity due to hemorrhage reduces the accumulation of interstitial fluid caused by histamine. It seems probable that endogenous catecholamines act directly on filtering vessels to lessen histamine-induced increases in permeability. However, a constriction of lymphatic vessels could have contributed to the reduction in lymph flow and we have no evidence against this possibility.