In patients receiving dopamine infusions for treatment of shock do free radicals convert dopamine to 6-hydroxydopamine?
Free hydroxyl radicals react with dopamine in vitro to produce the neurotoxin 6-hydroxydopamine (6-OHDA). If 6-OHDA were produced in vivo it could destroy central and/or peripheral neurons. Free radicals are produced in patients with cardiovascular or toxic shock. These patients are often treated with intravenous dopamine infusions. Using a newly developed method for measuring 6-OHDA in biological samples, we have examined blood from 15 patients receiving dopamine infusions for treatment of shock. 6-OHDA neither binds to nor elutes from either alumina or ion-exchange resins; therefore we used ODA-silica (Sep-Pak) to prepare samples for HPLC analysis with electrochemical detection. 6-OHDA disappeared rapidly from whole blood or serum at room temperature but was stable at -70 degrees C in an HClO4 extract. Recovery from Sep-Pak was 95% and detection limit 10 nmol/L. We repeated the experiments that showed in vitro hydroxyl radical conversion of dopamine to 5- and 6-OHDA. We detected neither 5- nor 6-OHDA in plasma samples from patients receiving dopamine infusions at 10-28 micrograms kg-1 min-1. Plasma dopamine in these patients was 1-5 mumol/L. We conclude that any 6-OHDA produced by hydroxyl radical attack in vivo is rapidly scavenged by endogenous substances containing sulfhydryl groups.
Tong
J
J
Diagnostic Research Laboratory, Toronto Hospital, Canada.
Baines
A D
AD
D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D004298:Dopamine / Q000008:administration & dosage / Q000378:metabolism / Q000627:therapeutic use*; D005609:Free Radicals / Q000097:blood; D006801:Humans; D007262:Infusions, Intravenous; D016627:Oxidopamine / Q000097:blood*; D012769:Shock / Q000097:blood / Q000188:drug therapy*
D005609:Free Radicals; D016627:Oxidopamine; D004298:Dopamine