title: Biosynthesis of platelet-activating factor. VI. Precursor of platelet-activating factor and acetyltransferase activity in isolated rat kidney cells.
abstract: Isolated glomeruli and tubular and medullary cells obtained from perfused kidneys from Wistar rats were stimulated with ionophore A 23187 (0.5 to 6 microM) or kept overnight at pH 9.5. The amount of platelet-activating factor (Paf-acether) formed was measured in the ethanolic cell extracts using aggregation of washed rabbit platelets. 2-Lyso Paf-acether present in cells was transformed into Paf-acether by chemical acetylation and measured in the same manner as Paf-acether. Microsomes from glomeruli and medullary and tubular cells were prepared, and the acetyltransferase activity was measured. Paf-acether was formed in a dose-dependent fashion by glomeruli and medullary cells, and maximal formation with 3 microM ionophore A 23187 was 1.9 +/- 0.2 and 1.1 +/- 0.2 pmoles/mg of protein, respectively. Paf-acether was not recovered from tubular cells. Three cell types produced large amounts of 2-lyso Paf-acether when incubated at alkaline pH. Only glomeruli generated appreciable quantity of 2-lyso Paf-acether upon ionophore A 23187 stimulation. The acetyltransferase specific activities in ionophore A 23187-stimulated glomeruli and medullary and tubular cells were 3.8 +/- 0.8, 0.3 +/- 0.1, and 0.2 +/- 0.1 nmoles of Paf-acether/10 min/mg of protein, respectively. This study demonstrates the formation of Paf-acether by two distinct populations of kidney cells, pointing out the glomerular cells, besides the already known medullary cells, as capable of forming Paf-acether.
mesh_terms: D000123:Acetyltransferases / Q000378:metabolism*; D000818:Animals; D066298:In Vitro Techniques; D007668:Kidney / Q000378:metabolism*; D007678:Kidney Glomerulus / Q000378:metabolism; D007679:Kidney Medulla / Q000378:metabolism; D007684:Kidney Tubules / Q000378:metabolism; D008297:Male; D008854:Microscopy, Electron; D010972:Platelet Activating Factor / Q000031:analogs & derivatives* / Q000096:biosynthesis* / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: C029271:O-deacetyl platelet activating factor; D010972:Platelet Activating Factor; D011498:Protein Precursors; D000123:Acetyltransferases; C027628:acetyl-CoA-1-alkyl-2-lyso-sn-glycero-3-phosphocholine acetyltransferase