Metabolic fate of platelet-activating factor in the rat enterocyte: the role of a specific lysophospholipase D.
The metabolism of platelet-activating factor (PAF) by isolated rat intestinal epithelial cells was investigated using 1-[3H]octadecyl-2-acetyl-sn-glycero-3-phosphocholine. The principal metabolite produced by the cells was 1-O-alkylglycerol, which was found in association with the cells and the medium. When similar studies were conducted employing an intestinal epithelial cell line (INT 407), PAF was almost quantitatively converted into 1-alkyl-2-acyl-sn-glycero-3-phosphocholine (AAGPC). When the intestinal epithelial cell microsomes were incubated in the presence of fluoride to inhibit phosphohydrolase activity, the formation of 1-alkylglycerol was decreased in association with a stoichiometric increase in 1-alkyl-glycerophosphate, indicating the presence of a lysophospholipase D in the intestinal cells. When the phospholipase D activity was examined in the microsomal fraction prepared from intestinal epithelial cells, lyso-PAF was the preferred substrate and only trace amounts of lyso-PAF were converted into alkylacyl-GPC. Acyllyso-GPC was rapidly cleaved to form free fatty acids. The absence of lysophospholipase D activity in INT 407 cells cannot be attributed to the absence of brush border in these cells since no lysophospholipase D activity was present in isolated brush border preparations.
Furukawa
M
M
Department of Biochemistry, University of Texas Southwestern Medical Center at Dallas 75235-9051, USA.
Muguruma
K
K
Frenkel
R A
RA
Johnston
J M
JM
D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000494:pharmacology; D002460:Cell Line; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D066298:In Vitro Techniques; D007421:Intestine, Small / Q000166:cytology / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology; D008861:Microsomes / Q000378:metabolism; D008871:Microvilli / Q000201:enzymology; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D010972:Platelet Activating Factor / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012969:Sodium Fluoride / Q000494:pharmacology; D013379:Substrate Specificity; D000099189:Lysophospholipase D
D002118:Calcium; D008274:Magnesium; D010727:Phosphoric Diester Hydrolases; D010972:Platelet Activating Factor; D012969:Sodium Fluoride; D000099189:Lysophospholipase D