Role of acidic ca++-independent phospholipase a2 in synthesis of
lung dipalmitoyl phosphatidylcholine.
Fisher, Aron B., and Chandra Dodia.
INSTITUTE FOR ENVIRONMENTAL MEDICINE, UNIVERSITY OF PENNSYLVANIA
MEDICAL CENTER, PHILADELPHIA, PA 19104
APStracts 3:0178L, 1996.
Dipalmitoylphosphatidylcholine (DPPC) synthesis by lung epithelium
occurs in part by a deacylation/reacylation pathway utilizing
phospholipase A2 (PLA2) and an acyl transferase. The role of acidic
Ca++-independent PLA2 (aiPLA2) in this pathway was investigated using
a transition state analogue enzyme inhibitor (MJ33, 1-hexadecyl-3
-trifluoroethylglycero-sn-2-phosphomethanol). Granular pneumocytes
were isolated from rat lung with elastase and maintained in primary
culture for 24 h on microporous membranes in the presence of
radiolabelled choline or free fatty acids (palmitate plus oleate).
Disaturated PC (DSPC) was determined by osmication chromatography.
Incorporation (nmol/mg protein) into DSPC at 24 h incubation was 11.9
+/- 0.2 for 3H-choline and 12.1 +/- 0.04 for 3H-palmitate. In the
presence of 3 mol % MJ33, incorporation of 3H-choline and 3H
-palmitate was decreased by 37% and 69%, respectively, and DSPC pool
size ([mu]g/mg cell protein) decreased by 9% (P<0.05). A
similar decrease in radiolabel incorporation was observed with 2 h
incubation. The presence of p-bromophenacylbromide (20 [mu]m) had a
significantly smaller effect that was additive with that of MJ33.
After 24 h labeling and 4 h chase with unlabelled substrate, there
was a significant decrease of radiolabel in DSPC which was inhibited
by MJ33. Under all experimental conditions, MJ33 resulted in either
no change or a modest increase of radiolabel in the cellular
unsaturated PC fraction. These results indicate that aiPLA2 has a
major role in DSPC synthesis by granular pneumocytes.
Received 1 August 1996; accepted in final form 27 September 1996.
APS Manuscript Number L245-6.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996