Phosphatidylethanol in Whole Blood of Rhesus Monkeys Correlates with Ethanol Consumption

BACKGROUND Phosphatidylethanol (PEth) homologs are ethanol metabolites used to identify and monitor alcohol drinking in humans. In this study, we measured levels of the two most abundant homologs, PEth 16:0/18:1 and 16:0/18:2, in whole blood samples from rhesus macaque monkeys that drank ethanol daily ad libitum to assess the relationship between PEth levels and recent ethanol exposure in this animal model. METHODS Blood samples were obtained from The Monkey Alcohol Tissue Research Resource. The monkeys were first induced to consume 4% (w/v) ethanol in water from a panel attached to their home cage. Then, monkeys were allowed to drink ethanol and water ad libitum 22 hours daily for 12 months and the daily amount of ethanol each monkey consumed was measured. Whole, uncoagulated blood was collected from each animal at the end of the entire experimental procedure. PEth 16:0/18:1 and 16:0/18:2 levels were analyzed by HPLC with tandem mass spectrometry and the ethanol consumed during the preceding 14 days was measured. Combined PEth was the sum of concentrations of both homologs. RESULTS Our results show that 1) PEth accumulates in the blood of rhesus monkeys after ethanol consumption; 2) PEth homolog levels were correlated with the daily average ethanol intake during the 14-day period immediately preceding blood collection; 3) application of established human PEth 16:0/18:1 cutoff concentrations indicative of light social and no ethanol consumption (< 20 ng/ml), moderate ethanol consumption (≥ 20 and < 200 ng/ml) and heavy consumption (≥ 200 ng/ml) predicted significantly different ethanol intake in these animals. PEth homologs were not detected in ethanol-naive controls. CONCLUSIONS This study confirms that PEth is a sensitive biomarker for ethanol consumption in rhesus macaque monkeys. This non-human primate model may prove useful to test for sources of variability previously shown between ethanol consumption and PEth homolog levels amongst humans.