COMPARISON OF METABOLITE LEVELS IN 2ND AND 3RD TRIMESTER HUMAN AMNIOTIC-FLUID SAMPLES USING PROTON MAGNETIC-RESONANCE SPECTROSCOPY

Objective: The objective of this study was to evaluate proton magnetic resonance as an analytical tool in the investigation of metabolites i n third trimester human amniotic fluid by comparison with literature v alues, including second trimester data. Methods: Normal human amniotic fluid from the third trimester has been examined using proton magneti c resonance spectroscopy at moderate field strength (300 MHz). Several small molecules were identified and quantitated using an external, ad ded standard. The mean values of the concentrations were compared with second trimester data obtained using nuclear magnetic resonance as we ll as with clinical chemistry literature values. Results: Third trimes ter concentrations were significantly lower for alanine, citrate, and glucose compared with second trimester. Acetate, creatine/creatinine, and lactate levels were not different. Histidine, tyrosine, and valine present in second trimester fluids at detectable amounts were very lo w and often not distinguishable from spectral baseline noise, Lactate was proposed as a possible internal standard for quantitation. Conclus ions: Proton magnetic resonance was shown to be an analytical tool of human amniotic fluid. The described technique did not allow for proper resolution in order to differentiate creatine/creatinine, The ratios of the mean concentrations between trimester samples using maleate and lactate as intensity references were in close agreement.