Intrinsic contractility of lymphatics in sheep and in dogs.

Abstract

Intralymphatic pressures were monitored from plastic cannulas implanted in the thoracic, lumbar trunk and mesenteric lymphatics of conscious and anesthetized sheep, and in the thoracic duct of anaesthetized dogs. Extrinsic factors appeared to be important in the propulsion of lymph only in the thoracic duct of the dog. Intrinsic pulsatile pressure patterns were recorded from all lymphatics studied in sheep, and from the thoracic duct in one out of three dogs. The pulses ranged from about 1–15 mm Hg in amplitude and from about 2–20 pulses/min in frequency. A parameter of contractility was defined and used to establish the existence in sheep of a linear relationship between contractility and flow rate. This relationship was demonstrated when flow was increased by infusion into the lymphatic or into a vein, or, in the case of mesenteric lymphatics, by feeding fat. It was concluded that the intrinsic contractility is myogenic in origin and is the major factor responsible for lymph propulsion at least in sheep; the relationship between contractility and flow enables the rate of lymph flow to keep pace with the rate of lymph production.