Abstract
Although norepinephrine and epinephrine are the predominant catecholamines (CAs) in peripheral tissues, peripheral dopamine (DA) systems are also physiologically significant. The DA is present both in the sympathetic ganglia and in the adrenal gland. We attempted to determine the possible presence of it in individual adrenal cells. We found increments in adrenal 3, 4-dihydroxyphenylacetic acid (DOPAC) levels produced by probenecid, an inhibitor of anionic secretory mechanisms. Small amounts of DA and DOPAC were detected in the rat adrenal gland by using the high-performance liquid chromatographic electrochemical detection method. Two hr after probenecid treatment (200 mg/kg, i.p.), the concentration of striatal homovanillic acid approximately doubled compared with those of control rats, and the levels of striatal DOPAC remained much the same. Conversely, the adrenal DOPAC was markedly increased with no change in the levels of CAs. The existence of DOPAC and the increase of DOPAC by probenecid indicate that the adrenal DA may be independently granulated.
