Dopamine metabolism in the rabbit carotid body in vitro: effect of hypoxia and hypercapnia.

Dopamine (DA) and noradrenaline (NA) were measured in the rabbit carotid body (CB) in vitro bv HPLC-ED under the following experimental conditions: 1h superfusion in normoxic, hypoxic (10% O2 in N2) or hypercapnic (8% CO2, 20% O2, 72% N2) medium, 5h superfusion in normoxia or hypoxia. The contents of DA and NA were decreased by hypoxia and hypercapnia after 1 h and 5h indicating a possible DA and NA secretion. Under the same experimental conditions synthesis of DA and NA and catabolism of DA were studied with enzymatic inhibition of tyrosine hydroxylase and monoamine oxidase (MAO) respectively. In hypoxia (1 h and 5h) the rate constant of DA synthesis was the same as in normoxia; however NA synthesis was decreased after 1 h hypoxia. On the contrary, hypercapnia, appeared to be a very effective stimulus of DA and NA synthesis.