ANALYSIS OF SATURATED PHOSPHATIDYLCHOLINE IN AMNIOTIC-FLUID BY P-31 NMR

A technique using solubilization with sodium cholate to resolve P-31 N MR resonances of phospholipid molecular species was applied to amnioti c fluid samples from 16 subjects. Gestational ages from 25 to 40 weeks were represented, and two subjects were sampled sequentially. Fitting of the partially resolved P-31 NMR signal of phosphatidylcholine (PC) generated an estimate of percent disaturated acyl PC (%dsPC) which co rrelated more highly with gestational age than did several other poten tial indices of fetal lung maturation, such as the ratio of PC to inor ganic phosphate from the solubilized spectra, or PC to sphingomyelin f rom extract spectra. In a few cases, enzyme-catalyzed PC hydrolysis li mited the precision, but did not appear to affect the accuracy, of the %dsPC estimates. Resolution of palmitoyl and oleoyl lyso-PC species w as observed for both the 1- and 2-acyl isomers. Upfield shifts due to the presence of cis double bonds in the lone acyl chain of the lyso-PC s were analogous to those observed for the diacyl PCs.