Synthesis of phosphatidylcholines in ozone-exposed alveolar type II cells isolated from adult rat lung: is glycerolphosphate acyltransferase a rate-limiting enzyme

Journal Article · Fri Jan 01 04:00:00 EST 1988 · Exp. Lung Res.; (United States)

DOI:https://doi.org/10.3109/01902148809062847· OSTI ID:5230985

Haagsman, H P; Schuurmans, E A; Batenburg, J J; van Golde, L M

Type II cells were exposed to ozone by gas diffusion through the thin Teflon bottom of culture dishes. The rate of phosphatidylcholine synthesis by type II cells, monitored by the incorporation of (Me-/sup 14/C)choline, was impaired by ozone at concentrations that did not affect other cellular parameters. The enzymes choline kinase and cholinephosphate cytidylyltransferase were not susceptible to inactivation by ozone at concentrations at which the activity of glycerolphosphate acyltransferase was decreased. The enzyme activity of lactate dehydrogenase increased after ozone exposure. The specific activity of choline kinase in the cytosolic fraction of type II cells was fivefold that in whole lung. The metabolism of (Me-/sup 14/C)choline was studied as a function of the choline concentration. Maximal rates of phosphatidylcholine synthesis were already attained at a concentration of 20 microM choline. Exposure of type II cells to ozone did not affect the recovery of label from (Me-/sup 14/C)choline in choline phosphate and CDP choline. However, the maximal rate of phosphatidylcholine synthesis decreased after ozone exposure, which indicates that the decreased apparent activity of glycerolphosphate acyltransferase limits the supply of diacylglycerols and thereby the rate of phosphatidylcholine synthesis. If the flux through the diacylglycerol pathway was stimulated by the addition of palmitic acid, a higher maximal rate of phosphatidylcholine synthesis was observed. The uptake of (Me-/sup 14/C)choline and the recovery of label in CDPcholine were not altered by the addition of different concentrations of palmitate. It is concluded that type II cells take up choline very efficiently, probably due to the high specific activity of choline kinase. At low choline concentrations the rate of phosphatidylcholine synthesis is determined by the supply of CDPcholine.

• Research Organization: Utrecht Univ. (Netherlands)
• OSTI ID: 5230985
• Journal Information: Exp. Lung Res.; (United States), Journal Name: Exp. Lung Res.; (United States) Vol. 14:1; ISSN EXLRD
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ALCOHOLS
AMINES
AMMONIUM COMPOUNDS
ANIMALS
BIOLOGICAL EFFECTS
BIOSYNTHESIS
BODY
CARBON 14 COMPOUNDS
CHOLINE
DRUGS
ENZYME ACTIVITY
ENZYMES
ESTERS
HEMIACETAL DEHYDROGENASES
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LACTATE DEHYDROGENASE
LIPIDS
LIPOTROPIC FACTORS
LUNGS
MAMMALS
METABOLISM
NUCLEOTIDYLTRANSFERASES
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
ORGANS
OXIDOREDUCTASES
OZONE
PHOSPHOLIPIDS
PHOSPHORUS-GROUP TRANSFERASES
QUATERNARY COMPOUNDS
RATS
RESPIRATORY SYSTEM
RODENTS
SYNTHESIS
TRACER TECHNIQUES
TRANSFERASES
VERTEBRATES