Figure 8

Molecular specificity of newly synthesised major bronchoalveolar lavage surfactant phosphatidylcholine fraction in ARDS patients over time (A), endogenous and methyl -D ₉ labelled fractional composition of PC16:0/16:0 for both controls and patients (B), endogenous and methyl -D ₉ labelled fractional composition of PC16:0/16:0 for individual controls (C) and patients (D) at 48 hours after methyl -D ₉ -choline infusion. At the earliest time point (T = 06 Hrs) after methyl-D₉ choline infusion, unsaturated PC species predominate with subsequent gradual increase in PC16:0/16:0 over time. PC16:0/16:0 synthesis, expressed as a percentage of newly-synthesised total PC, was compared with that of endogenous PC16:0/16:0 at two time points for controls and six time points for patients. The proportion of methyl-D₉-labelled PC16:0/16:0 was significantly lower than that of unlabelled PC16:0/16:0, when both are expressed relative to total labelled and unlabelled PC pools, and at 24 hours this deficit is greater in ARDS compared with control subjects. For both patients and controls, the newly synthesised fraction of PC16:0/16:0 was in equilibrium with endogenous composition at 48 hours after methyl-D₉ choline infusion. Presented as mean ± SEM; † P < 0.05. There is considerable variation in the relative proportion of fractional labelling of PC16:0/16:0 in patients compared to the controls in addition to lower fractional synthesis of PC16:0/16:0 in 3 patients (P02, P04 and P08) compared with endogenous fraction. Controls (n) =9 and patients (n) =9. PC, phosphatidylcholine. C, individual controls; P, individual patients.