Oxygen pressure in small lymphatics.

Oxygen tension of the small lymph vessels (PLO2) of the rabbit hind limb was measured with both a flow-through micro chamber and a polarographic catheter-tip oxygen electrode to obtain experimental data on the source of oxygen in the lymph. The following processes may influence PLO2: 1. Since the structure of the lymphatic capillaries allows a free diffusion of small molecules from the interstitial fluid into the lymphatics the lymph within its capillaries can mirror the oxygen supply of the tissue, i.e., probably a mean interstitial PO2. 2. PLO2 might be influenced by the oxygen content of the tissue surrounding the lymph vessels. Measurement with the catheter electrode showed that PLO2 rose after superfusing vessel with O2-saturated saline. After occlusion of the artery running paralled to the lymph vessel, a decrease in PLO2 was recorded. PLO2 in the absence of lymph flow increased rapidly after O2 inhalation. This reaction could be impeded by occluding the artery running parallel with the lymph vessel. 3. The mean oxygen tension of the prenodal (afferent) lymph measured with the flow-through chamber was 28.1 +/- 12.0 torr, whereas that measured with the catheter electrode was 42.0 +/- 12.18 torr. This difference may be attributed to the oxygen consumption of the lymph cells. The lymph containing a large number of cells has a stronger oxygen consumption than that with a lower number of cells. These observations suggest that PLO2 is influenced not only by the oxygen tension of the tissues drained by the lymph but also by the oxygen consumption of lymph cells as well as by the oxygen content of the surrounding tissues and perhaps by that of the blood vessels which are located at different distances from the collecting lymphatic vessels.