Proceedings of The Physiological Society

Physiology 2016 (Dublin, Ireland) (2016) Proc Physiol Soc 37, PCB316

Poster Communications

Action of somatostatin and analogues on human lymphatic vessels

F. T. Skov1, V. E. Hjortdal2, D. B. Bødtkjer1

1. Biomedicin, Aarhus university, Aarhus C 8000, Midjylland, Denmark. 2. Cardiothoracic and Vascular Surgery, Aarhus University Hospital Skejby, Aarhus, Denmark.

Lymph is actively transported from lymphatic capillaries to the venous circulation by intrinsic contractile activity in the collecting lymphatic vessels. The largest collecting lymphatic is the thoracic duct (TD), which terminates into the veins of the neck. Accumulation of lymph in the thorax (chylothorax) caused by damage to the TD occurs in congenital heart diseases, e.g. univentricular circulation, as well as in connection with thoracic operations or trauma. With protracted chylothorax pharmacological options are desired to resolve this problem more quickly. Since the first reports of somatostatin (SST) infusion to treat chylothorax, many clinicians worldwide have treated patients with SST or its stable synthetic analogue octreotide. The therapeutic rationale is that SST or octreotide reduce lymph production: we hypothesize that an additional direct action of SST on lymphatic contractility also occurs. To investigate SST reactivity we use isolated lymphatic vessels; thoracic duct (from oesophagus cancer) and intestinal lymphatics (from gastric bypass) mounted in wire myographs for isometric force measurement. Spontaneous, non-spontaneous and electric field-stimulated (EFS) contractile activity are studied in vessels normalized to a transmural pressure of 21 mmHg. After equilibration vessels are challenged by acute and prolonged incubations with somatostatin (SST-14 and -28) and octreotide. Results to date suggest that the acute exposure we test in our system does not decrease contraction frequency but rather tends to stimulate rate of activity, while force remains unchanged. Interestingly, some quiescent vessels were also activated with 10nM Oct (P=0.09) and 10nM SST-14 (P=0.17). The EFS experiments revealed no effect on nerve-stimulated contraction for any of the drugs. We conclude that human lymphatic vessels respond to acute SST exposure by increased activity, which would be contrary to reducing lymph flow in vivo in treatment of chylothorax. However, we cannot yet conclude what effect chronic exposure in vivo could have on lymphatic pumping ability.

Where applicable, experiments conform with Society ethical requirements