ABSTRACT
I. Introduction 3
II. Composition of Surfactant Phospholipid Molecular Species in
the Adult Lungs 6
III. Molecular Species of Surfactant Phospholipid During Fetal
Development 9
IV. Molecular Species of Phospholipid During Postnatal
Development 9
V. Modification of Surfactant Phospholipid Molecular Species in
Disease States 10
A. Respiratory Syncytial Virus Bronchiolitis 10
B. Respiratory Diseases in Children 10
C. Asthma 11
D. Acute Respiratory Distress Syndrome 11
VI. Conclusion 12
References 12
I. Introduction
The importance of the phospholipid component for the physiological function of
lung surfactant has been recognized for many years. However, the effects of
development and disease on the detailed phospholipid composition of surfactant
have received relatively little attention until recently, largely because of lack of
sensitivity and specificity of the analytical methods available. Phospholipids
are characterized either as glycerophospholipids, with fatty acids esterified at
the sn-1 and sn-2 positions of the glycerophosphate backbone of the molecule,
or as sphingolipids, with a fatty acid esterified to a sphingosine phosphate
moiety (Fig. 1.1). The head group attached to the phosphate of glycerophospho-
lipids can be choline, ethanolamine, serine, glycerol, or inositol to give, respect-
ively, phosphatidylcholine (PtdCho), phosphatidylethanolamine (PtdEtn),
phosphatidylserine (PtdSer), phosphatidylglycerol (PtdGly), or phosphatidyl-
inositol (PtdIns). The vast majority of sphingolipids have choline esterified to
the phosphate to generate sphingomyelin. Within each of these phospholipid
classes, there is a spectrum of individual molecular species, defined by the com-
bination of esterified fatty acids attached to the glycerol. Generally, membrane
glycerophospholipids tend to have palmitoyl (16:0)1 or stearoyl (18:0) at their
sn-1 position and unsaturated fatty acids esterified at sn-2. The esterified fatty
acid in sphingolipids is generally saturated, but can often contain as many as
22 or 24 carbon atoms.
