The histology of the carotid bodies in highlanders from Ladakh

A histological study was made of the carotid bodies in a boy and three adult male highlanders born and residing between altitudes of 3300 m to 4200 m in Ladakh. The carotid bodies were enlarged in two of the men, and in all four subjects showed increased numbers and enlargement of the dark variants of the chief cells of the glomic tissue. In these dark cells the cytoplasm was voluminous, formed streamers and contained many intracytoplasmic vesicles of which some had mused to form larger vesicles that appeared to have discharged from the cell surface. Immunohistochemical studies showed that these cells contained considerable amounts of the peptide met-enkephalin. It is thus considered that prominence of dark cells containing this peptide is characteristic of sustained exposure of the carotid bodies to hypobaric hypoxia. In the middle-aged highlander there was a prominence of sustentacular cells which encroached upon the cores of chief cells and this may be associated with the characteristic loss of hypoxic ventilatory response in the highlander.