The antihypertensive drug DL-propranolol inhibits the vascular changes in rat carotid body during long-term hypoxia.

Rats were exposed to hypoxia (10% O2) for 1 and 3 weeks with or without daily injections of DL-propranolol (0.66 mg/kg i.p.). The structure of the carotid bodies was analyzed by light microscopical morphometry. Hypoxia induced enlargement of the carotid body due to enhanced vascularity and hypertrophy of glomic and interstitial tissues. The contents of dopamine and norepinephrine multiplied. Propranolol abolished the vasodilatory effect of hypoxia within the first week but did not prevent the other structural changes and the rise in catecholamine content. The data suggest that 1) the vaso-dilation elicited by long-term hypoxia may be controlled by beta-adrenoceptors; 2) the structural and biochemical events occurring in rat carotid body during long-term hypoxia seem to be controlled by different mechanisms.