Erythropoietin in renal and hepatic lymph of conscious ewes

Spontaneously flowing fistulae were established in the efferent lymphatics of popliteal, prescapular and prefemoral nodes and lumbar trunk or in the afferent lymphatics draining the kidney and liver of sheep. Lymph was collected from these sites over various time intervals and assayed for erythropoietin (Ep) content. The objective of the study was to establish the anatomic site(s) of Ep production. Normal lymph did not contain detectable titers of Ep, nor did renal lymph or blood plasma from a sheep systematically treated with cobaltous chloride. Renal lymph did contain measurable levels of Ep following renal artery constriction, unilateral hydronephrosis or phenylhydrazine-induced hemolytic anemia. Phenylhydrazine treatment also produced elevated Ep levels in lymph from the liver but not in lymph efferent from either popliteal or prescapular nodes. These results indicate that Ep is generated primarily in the kidney and that the liver may be an extrarenal source of the hormone. The surgical techniques used in this study offer distinct advantages in examining the composition and physiology of lymph in sheep.