Direct measurement of dopamine O-sulfate in plasma and cerebrospinal fluid

This paper describes a method for measurement of dopamine 3-O-sulfate (DA3S) and dopamine 4-O-sulfate (DA4S) in dog and human plasma and dog cerebrospinal fluid. C18 solid-phase extraction columns were utilized for sample preparation. DA3S and DA4S were separated by high-performance liquid chromatography and then quantified by dual-electrode electrochemical detection. [3H]Dopamine O-sulfate (DAS) was used as internal standard. Recovery of authentic DAS added to dog plasma and carried through the entire procedure was 49.9 +/- 6.3% for DA3S (n = 9) and 42.2 +/- 4.3% for DA4S (n = 8). The lower limit of detection (signal-to-noise ratio of 3) was 20 fmol for each DAS isomer. The within-assay coefficient of variation for DA3S in dog plasma averaged 5.8% (range 2.0-12%, n = 5). The between-assay coefficient of variation for DA3S in dog plasma was 3.8% (n = 3). DAS levels in plasma of conscious dogs were 20.3 +/- 6.9 pmol/ml DA3S and 5.91 +/- 3.5 pmol/ml DA4S (n = 5). Cerebrospinal fluid levels were 3.06 +/- 3.22 pmol/ml DA3S and 0.10 +/- 0.18 pmol/ml DA4S in dogs anesthetized with methoxyflurane and nitrous oxide (n = 3). This procedure is also appropriate for use with human plasma; DAS levels were 24.3 +/- 12.8 pmol/ml DA3S and 9.07 +/- 3.9 pmol/ml DA4S (n = 6).