Effect of norepinephrine on lymph flow and edema formation in the canine forelimb.

In the present study we sought evidence for the hypothesis that norepinephrine (NE) can cause constriction of lymph vessels in the canine forelimb perfused at constant flow. Mechanical venous compression (small-vein pressure approximately equal to 45 mmHg), intra-arterial infusion of histamine (16 micrograms base/min), and intra-arterial infusion of NE (16 micrograms base/min) caused the limbs to gain weight at similar rates due to edema formation; the first two maneuvers caused a sustained increase in skin lymph flow, but the increase in lymph flow with NE was only transient. Similar changes were seen during infusion of NE at 1 and 2 micrograms/min, and studies with radioactive microspheres indicated that NE increased capillary blood flow. When venous pressure was elevated and held constant at 45 mmHg. NE (4 micrograms base/min ia) antagonized and phentolamine (400 micrograms/min ia) potentiated the increase in skin lymph flow. Finally, NE (16 micrograms base/min ia) caused a reduction in histamine (16 micrograms base/min)-elevated skin lymph flow, despite the fact that capillary pressure was greatly increased due to active venous constriction. We conclude that intra-arterial infusion of norepinephrine in the dog forelimb perfused at constant flow causes constriction of lymphatic trunk vessels in skin, resulting in increased resistance to the flow of lymph.