Intact and sympathectomized carotid bodies of long-term hypoxic rats. A morphometric light microscopical study.

Intact and sympathectomized carotid bodies from rats exposed to hypoxia (room-air mixed with N2 to a final oxygen concentration of 10%) for 1, 2 and 3 weeks were analyzed by morphometric methods using the light microscope. Exposure to hypoxia enlarges the carotid bodies, in which the vascularity increases dramatically from the first week. This changed vascularity seems to be due to enhanced vasodilatation. In addition, there is a pronounced profileration of the endothelial tissue, thus suggesting an ingrowth of new blood vessels. The volume density of glomic type I, and type II cells, decreases during hypoxia but when calculated in total volumes this entity is increased 3-fold. Sympathectomy does not modify the structural changes occurring during hypoxia when compared with carotid bodies with intact innervation. Though the primary elements in the mechanism of transduction in carotid body are unknown, a remodelling of the vascular architecture may be a method by which this chemoreceptor alters its sensitivity.