The paraganglia within the carotid bifurcation regions of young and old spontaneously hypertensive rats (SHR) after exposure to chronic hypobaric hypoxia. I. The carotid bodies.

Carotid body volumes and the histological appearance of these chemoreceptors were studied using light microscopic methods in 10 groups of spontaneously hypertensive rats (SHR). The aim of this study was to clarify the influence of chronic hypobaric hypoxia on the carotid bodies of SHR depending on the age of the rats, on the duration of exposure to hypoxia, and on different salt intake, respectively different blood pressure. We found that: 1. The carotid bodies of chronically hypoxic SHR are enlarged. 2. The degree of carotid body enlargement is dependent on the duration of exposure to hypoxia. 3. In old SHR the increase of carotid body volume was smaller than in young SHR. 4. Old chronically hypoxic SHR exhibited more distinct vascular changes in the carotid bodies than age-matched normoxic controls as well as younger chronically hypoxic and normoxic SHR. 5. The influence of different levels of systemic arterial blood pressure on the carotid body volumes was rather small compared with the effects of chronic hypobaric hypoxia.