Collecting lymphatic vessel permeability to albumin and its modification by natriuretic peptides

Macromolecules and water leave the blood microcirculation and bathe the tissues of the body, and cannot be constitutively reabsorbed by the blood vessels, necessitating an outflow pathway that is comprised by the lymphatic vasculature. The mechanisms underlying the transport of macromolecules and water to or from the lymphatic vessels have not been elucidated fully until now, due to the difficulty in manipulating these structures. Here we demonstrated that the microfluorometric technique designed to assess blood capillary solute permeability (Ps) could be modified to determine the Ps of single collecting lymphatic vessels. Lymphatic endothelium has recently been shown to be derived from the cardinal vein, suggesting that these endothelial types share many genes, thus functions; we hypothesized that collecting lymphatic and venular Ps, as well as its response to natriuretic peptides, do not differ. In accordance, we demonstrated that the median lymphatic and venular Ps to albumin did not differ, nor did their diffusive permeabilities (Pd) or estimated hydraulic conductivities (Lp). Follow-up studies were then performed to determine whether protein was absorbed or expelled by collecting lymphatics, and revealed that collecting lymphatic vessels possessed concentration