Adrenal response to long-term hypoxia is still increased after carotid body denervation in rat

This study investigated the effects of long-term normobaric hypoxia (10% O2 in N2 for 2, 7, 14, and 28 days) on the metabolism of catecholamines in rat adrenals and the role of the carotid body chemoreceptors in the adrenal response. The content and utilization of dopamine were significantly increased from the 7th day of hypoxia and remained enhanced thereafter. The content of norepinephrine and epinephrine decreased after 2 days of hypoxia and increased thereafter; after 28 days of hypoxia the norepinephrine amounts remained enhanced but the epinephrine levels were no longer significantly increased. In vivo tyrosine hydroxylation increased after 7 days of hypoxia. Bilateral transection of the carotid sinus nerve 1 wk before hypoxia failed to abolish the increase in the content and utilization of dopamine after 7, 14, or 21 days of hypoxic exposure. These results indicate that long-term normobaric hypoxia elicits a long-lasting increase in the metabolism of catecholamines in adrenals, especially as assessed by dopamine measurement, and that this response does not involve a carotid body chemoreflex pathway.