Abstract
The amounts of endogenous dopamine (DA) in rabbit atria and arteries were less than 7% of total catecholamine content. Renal artery had the highest concentration of DA (0.30 μg/g), and the ratio of DA to noradrenaline (NA) was the largest among the tissues examined. After a single dose of reserpine (1 mg/kg i.p.), the levels of NA in the atria, mesenteric and renal arteries were reduced markedly, whereas the reduction of DA in the latter two arteries was not significant, suggesting that some of the DA is localized in the cytoplasm by a reserpine-resistant mechanism in these arteries. The uptake of 3H-DA or 3H-(/)-NA after incubation with 0.1 μM 3H-amine was the largest in the renal artery. After incubation with 3H-DA, the production of oxidative deaminated metabolites was 2-3-fold higher than that after with 3H-NA despite the smaller uptake of total 3H, suggesting that DA may not always be taken up by the vesicles or that this compound may be leaked from the vesicles into the cytosol more readily than NA and degraded by monoamine oxidase. Electrical transmural stimulation after incubation of renal artery with 14C-DA increased the overflow of both 14C-DA and 14C-NA, demonstrating the importance of the storage, conversion and release mechanism in this artery.
