BIOSYNTHESIS OF PLATELET-ACTIVATING FACTOR .6. PRECURSOR OF PLATELET-ACTIVATING FACTOR AND ACETYLTRANSFERASE ACTIVITY IN ISOLATED RAT-KIDNEY CELLS

  • 1 January 1984
    • journal article
    • research article
    • Vol. 51  (5) , 567-572
Abstract
Isolated glomeruli and tubular and medullary cells obtained from perfused kidneys from Wistar rats were stimulated with ionophore A 23187 [calcimycin] (0.5 to 6 .mu.M) 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 .mu.M ionophore A 23187 was 1.9 .+-. 0.2 and 1.1 .+-. 0.2 pmol/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 a 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 2 distinct populations of kidney cells, pointing out the glomerular cells, besides the already known medullary cells, as capable of forming Paf-acether.

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