PAF-ACETHER-INDUCED PLASMA EXUDATION IN RAT SKIN IS INDEPENDENT OF PLATELETS AND NEUTROPHILS

  • 1 January 1984
    • journal article
    • research article
    • Vol. 1  (1) , 107-122
Abstract
The ability of Paf-acether to induce increased plasma protein extravasation (IPPE) was assessed in the skin of rats by measuring extravasation of 125I-bovine serum albumin. Paf-acether elicited dose-dependent IPPE with a threshold of 0.04 pmol and a maximum at 4.5 nmol, with an effective concentration (EC50) of 23 pmol. The EC50 of the 1-O-ester Paf-acether analog was 1.5 mol whereas 2-lyso Paf-acether was ineffective in inducing IPPE. Serotonin and histamine were respectively 100 and 1,000-fold less potent than Paf-acether. High doses of Paf-acether also resulted in a dose related accumulation of III-indium oxine labeled platelets. Ultrastructural and radioisotopic studies showed that Paf-acether-induced IPPE was not dependent upon platelet accumulation. In addition, platelet release products were ruled out in this phenomenon, since a "cocktail" of indomethacin, methylsergide and pyrilamine-maleate failed to significantly reduce Paf-acether-induced IPPE. Neutrophils were not involved in Paf-acether-induced IPPE since nitrogen mustard-treated animals presented with IPPE not significantly different from controls. Finally, the specificity of Paf-acether on IPPE formation was demonstrated by its complete prevention by prior intravenous injection of Paf-acether (6 .mu.g/kg), but not of Paf-acether analogs, histamine or serotonin.

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