Phosphatidylethanol - formation and degradation in blood and organs

Abstract: Phosphatidylethanol (PEth) is an abnormal phospholipid formed exclusively by the action of phospholipase D (PLD) in the presence of ethanol. The degradation of PEth is slow and due to its accumulation in some cells the possibility to use PEth as marker of ethanol intake has been proposed. It has also been suggested that PEth mediates some of the damaging effects of ethanol on cells. This study was made to investigate the formation and degradation of PEth, after ethanol exposure, in organs, blood, and cell-lines from animals and humans both in vivo and in vitro. After different in vivo alcohol exposures, the level of PEth accumulated in organs of rats was measured. Blood from humans, rats, a pig and a ferret was also incubated in vitro with ethanol for investigation of the PEth formation. The degradation of PEth was studied in human blood and in two cell-lines in vitro. PEth content in organs and blood from cadavers of alcoholics was measured. The effect of storage conditions on PEth content in blood and organs was studied. PEth was measured in blood from two groups of alcoholic patients and related to the ethanol intake and to three clinically available markers of chronic ethanol intake. PEth was analysed by high performance liquid chromatography (HPLC) and evaporative light scattering detection. The analytical method for PEth was improved by using internal standard, and by modifying the extraction method the limit of quantification could be lowered. Rats exposed to ethanol acutely or chronically formed PEth in most of their organs. The amount of PEth formed in the organs varied, and it was shown that both the differences in type of exposition, and ethanol concentrations, are of importance. Also the rate of PEth degradation varied among the organs. No in vivo PEth formation occurred in the rat blood. PEth was formed in human blood incubated in vitro with ethanol. However, in blood from rat, pig, and ferret, no PEth formation occurred in vitro. PEth formation in human blood in vitro was linear with time and ethanol concentration dependant; individual variation in formation rate was demonstrated. No degradation of PEth could be observed in human blood during 48 hours in vitro. Very high PEth concentrations were found in organs and blood from the autopsied alcoholics, probably due to formation of PEth during freezing at –20°C. Storage of rat organs and human blood at –20°C with ethanol present highly elevates PEth levels. Rat organs and human blood without ethanol present can be frozen at –20°C without affecting PEth levels. In blood from alcoholics PEth had a diagnostic sensitivity of 100% in inpatients and 98% in outpatients. The sensitivity of the other markers varied between 28% and 77%. PEth, CDT, and GGT correlated to ethanol intake with the strongest correlation found for PEth. Thus PEth is highly correlated to ethanol intake and the present results indicate that the diagnostic sensitivity is higher than in previously established alcohol markers.