The Carotid Body as a Neuroendocrine Organ Involved in Control of Erythropoiesis

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Abstract
The carotid body is generally regarded solely as a chemoreceptor. This paper presents evidence that the carotid body is also an endocrine gland, secreting one or more erythropoiesis-controlling hormones. Its removal is followed by anemia and by a lack of reticulocyte response to daily bleeding. The removal of both carotid bodies results in a reduction of the high reticulocyte count induced by daily bleeding (5-40% of erythrocytes) down to 0.1% of erythrocytes. The injection of an extract of the carotid body causes reticulocytosis within 5 hr. This reticulocytosis attains its peak 48-72 hr after injection. Daily bleeding for 15 days produces an increase in weight of the carotid body and ultrastructural alterations that indicate increased protein synthesis in the main cells. The injection of plasma from efferent blood from the carotid body into either normal cats or cats from which both carotid bodies have been removed is followed within 6 hr by the appearance of large numbers of reticulocytes and macroreticulocytes in peripheral blood. Carotid body extracts and efferent blood plasma exhibited erythropoietin activity, which was demonstrated in the polycythemic rat by the (59)Fe incorporation method.