Effect of serotonin, epinephrine, histamine, and hexamethonium on thoracic duct lymph

Abstract

Serial studies of thoracic duct lymph flow rates and lymph proteins including albumin, globulin and fibrinogen were performed in 22 fasting unanesthetized dogs following intrathoracic cannulation of the thoracic duct with a polyethylene catheter. Serotonin given intravenously (20 µg/kg/min) produced a marked increase in lymph flow (115%) with a 20% decrease in total protein concentration. A single intravenous injection of epinephrine (1 mg) produced a 92% increase in lymph flow accompanied by a 12% increase in protein concentration. Histamine (1 mg) given intravenously also produced a significant increase in lymph flow (127%) but protein concentration remained constant. Hexamethonium chloride (2.5 mg/kg iv) markedly depressed lymph flow rate (50%) without significantly altering lymph protein concentrations. The possible mechanisms of action of each of these agents is discussed. Results indicate that serotonin markedly influences lymph production and lymph protein concentration by a probable selective alteration of capillary permeability rather than by increasing intestinal motility.