PLASMALOGENS EFFECTIVELY REDUCE THE SURFACE-TENSION OF SURFACTANT-LIKE PHOSPHOLIPID MIXTURES

The alkenyl-acyl subclass of phosphatidylethanolamine (PtdEtn) and pho sphatidylcholine (plasmalogens) are minor components of alveolar surfa ctant. Plasmalogens promote and stabilize hexagonal structures of phos pholipids. In another study (W. R. Perkins, R. B. Dause, R. A. Parente , S. R. Michey, K. C. Neuman, S. M. Gruner, T. F. Taraschi, and A. S. Janoff. Science 273: 330-332, 1996), it was shown that polymorphic pha se behavior may have an important role in the effective functioning of pulmonary surfactant. Therefore, we hypothesized that surface propert ies of phospholipid mixtures that contain plasmalogens are superior to plasmalogen-free mixtures. The effect of plasmalogens on surface tens ion of surfactant-like phospholipid mixtures (70 mol% dipalmitoyl phos phatidylcholine, 10 mol% phosphatidylglycerol, and 20 mol% PtdEtn) was measured. Using the pulsating bubble surfactometer, we show that an i ncreasing amount of ethanolamine plasmalogens [plasmenylethanolamine ( PlsEtn)] results in reduction of surface tension (0 mol% PlsEtn 44.7 /- 1.7, 2 mol% 33.5 +/- 1.7, 4 mol% 36 +/- 3.1, 6 mol% 26.2 +/- 2.9, a nd 8 mol% 22.2 +/- 0.3 mN/m). By means of the captive bubble surfactom eter, minimal surface tension reached with 8 mol% PlsEtn was even lowe r (3.8 +/- 0.7 mN/m). With regard to morphological studies (B. Fringes , K. Gorgas, and A. Reith. Eur. J. Cell Biol. 46: 136-143, 1988), clof ibrate treatment of rats might increase the plasmalogen content of alv eolar surfactant. However, in the present study, we could not show tha t synthesis and secretion of plasmalogens are affected by clofibrate t reatment.