B. Anderstam et al., A LUMINOMETRIC ASSAY FOR DETERMINATION OF ETHANOL IN MICRODIALYSATES, Scandinavian journal of clinical & laboratory investigation, 58(1), 1998, pp. 89-96
In microdialysis, samples from the extracellular fluid are analysed in
the outgoing dialysate. By adding ethanol to the ingoing perfusate an
d following its exchange in the dialysate, an outflow/inflow ratio is
obtained. This ratio has been shown to correlate with the tissue blood
flow. An automatic luminometric ethanol assay that quantifies the lig
ht produced from three coupled enzyme reactions is described. Alcohol
dehydrogenase catalyses the oxidation of ethanol with formation of NAD
H, which is monitored using NADH:FMN oxidoreductase and bacterial luci
ferase. Each assay can be individually calibrated by measuring the inc
reased rate of NADH formation through the addition of a known amount o
f ethanol. The linear range of the assay was 0.05-10 mmol l(-1) in mic
rodialysate samples. The within-run imprecision was 1.4% CV in 10 mmol
l(-1) samples, and ethanol recovery was almost 100%. The assay was ap
plied to microdialysates that were generated from probes implanted in
the vastus lateralis muscle in fasting subjects (n=12) and perfused wi
th 5 mmol l(-1) ethanol at 3 mu l min(-1). An outflow/inflow steady-st
ate ratio of 27% (range 19-47%) appeared after about 1 h, followed by
a within-run variability of 4.7% CV (range 2.5-7.7% CV), as calculated
from samples collected every 15 min up to 4 h after stabilization. In
conclusion, a sensitive ethanol assay, suitable for studies of microc
irculatory exchange of solute molecules over the dialysis probe is pre
sented.