Studies on the formation of dipalmitoyl species of phosphatidylcholine and phosphatidylethanolamine in pulmonary type II cells

Abstract

Endogenous content of and incorporation of labelled glycerol into alkenylacyl-, alkylacyl-and diacyl-glycerol, -glycero-3-phosphocholine and -glycero-3-phosphoethanolamine of pulmonary type II cells were measured. On prolonged incubation of type II cells with labelled glycerol, the proportion of label incorporated into the diacyl subclass of these glycerolipids increased and the proportion of label incorporated into the ether lipids declined. Endogenous phosphatidylcholine (PtdCho) of type II cells contained 38.40 of the dipalmitoyl species, but endogenous phosphatidylethanolamine (PtdEtn) only 2.5 %. In contrast, similar proportions of labelled glycerol were incorporated into dipalmitoyl-PtdCho and -PtdEtn after short-time incubation but, with prolonged incubation time the proportion of labelled dipalmitoyl-PtdCho increased from 11.3 to 18.8 %, whereas that of dipalmitoyl-PtdEtn did not change significantly. Type II cell membranes were found to exhibit cofactor-independent and CoA-mediated transacylations of [1_-4C]palmitoyl-lyso-PtdCho and -lyso-PtdEtn. The distribution of label among the palmitic acid-containing species of PtdCho and PtdEtn formed by both transacylation activities was determined. Cofactor-independent and CoA-mediated transacylation showed a strong selectivity for palmitate and arachidonate and a strong discrimination against oleate. The amount (nmol) of dipalmitoyl-PtdEtn formed by both transcylation activities after short-time incubation (2 min) decreased with prolonged incubation time (60 min). In contrast, the nmol of dipalmitoyl-PtdCho formed by cofactorindependent transacylation remains nearly the same after short-time and longer incubation. The nmol of dipalmitoylPtdCho formed by CoA-mediated transacylation increased strongly in the same time interval. Beside synthesis de novo via the CDP-choline pathway and reacylation of lyso-PtdCho with palmitoyl-CoA, the CoA-mediated transacylation of lyso-PtdCho may be an effective pathway for the formation of dipalmitoyl-PtdCho in pulmonary type II cells.

Time-dependent changes in pulmonary surfactant function and composition in acute respiratory distress syndrome due to pneumonia or aspiration

“…The profile of molecular species of phosphatidylcholine from large surfactant aggregates was analyzed after phospholipolytic cleavage of the polar headgroup with phospholipase C and conversion of the resulting diradylglyceroles (DRG) to naphthylurethanes by means of high performance liquid chromatography (HPLC) following a variation of the method described by Rüstow et al [28]. Due to a lack of material, PC molecular species were only calculated in 10 out of 15 patients.…”

Surfactant abnormalities after single lung transplantation in dogs: impact of bronchoscopic surfactant administration

“…The profile of molecular species of PC was analyzed following phospholipolytic cleavage of the polar head group with phospholipase C and conversion of the resulting diradylglyceroles with 1-naphthylisocyanate by means of high-performance liquid chromatography following a variation of the method described by Ruestow and colleagues. 18 SP-B and SP-C were quantified using recently described enzyme-linked immunosorbent assay techniques, 19,20 with isolated canine SP-B and SP-C 21 serving as standard. For characterization of relative content of large surfactant aggregates (LSA) and surface activity, bronchoalveolar lavage fluid (BALF) was centrifuged at 48,000g (1 hour, 4°C), the pellet was resuspended in a small volume of 0.9% NaCl containing 3 mmol/L CaCl 2 and assessed for the phospholipid (PL) content.…”

Diacylglycerol species as messengers and substrates for phosphatidylcholine re-synthesis during Ca2+-dependent exocytosis in boar spermatozoa

“…It could be argued that other mechanisms, such as PE or PS conversion to PC, acylation of lysoPC, or transacylation of two lysoPCs (Pelech and Vance, 1984;Bishop and Bell, 1988;Rü stow et al, 1992), may also participate in the re-synthesis of PC seen in spermatozoa. However, none of them can explain our results.…”