Carotid body, adrenal medulla and Zuckerkandl organ as an integrated sympathoadrenal system in human prenatal development

Introduction. The cells in adrenal medulla, carotid body and the organ of Zuckerkandl have the common origin from the neural crest. Nevertheless, despite the similarity in both histological and biochemical characteristics of these organs, contemporary scientific paradigm contrasts the carotid body with the adrenal gland and the organ of Zuckerkandl. The adrenal gland and the organ of Zuckerkandl are considered to function as endocrine glands whereas carotid body is thought to be a chemoreceptor organ. The endocrine function of the carotid body is still in question. The aim of the work was to evaluate the possibility of the presence of endocrine function by the carotid body in the embryonic, prefetal and early fetal period of human development by immunohistochemistry and compare it with the function of the organ of Zuckerkandl and the adrenal medulla. Materials and methods. The study was performed on 5 fetal autopsies (gestational age 8–20 weeks) using immunoperoxidase labeling with antibodies to bIII-tubulin, tyrosine hydroxylase, synaptophysin and PGP9.5. Results. In all samples of the carotid body, the organ of Zuckerkandl and the adrenal medulla, the cells showed a positive reaction to all the markers. All carotid bodies showed very high TH/bIII ratio approaching unity. The organ of Zuckerkandl in all fetus showed much higher TH/bIII ratio than that inthe carotid body. In the adrenal glands at 11–20 weeks of gestation TH/bIII ratio was even greater. In the adrenal gland in 8-week embryo this ratio was lower than in the carotid body. Conclusion. We have showed that the number of TH-positive cells in the carotid body in the embryonic and early fetal periods is much higher than in postnatal period. Our data may indicate endocrine function of the carotid body during the antenatal period of development. Thus, the carotid body is likely to synthesize catecholamines while the adrenal medulla is functionally immature and cannot support the body’s homeostasis. Keywords: sympathoadrenal system, human development, carotid body, organ of Zuckerkandl, adrenal gland.