Inhibition by dietary tea polyphenols of chemical mediator release from rat peritoneal exudate cells

Male Wistar rats were given purified diets containing safflower (SAF), peri lla (PER), or palm (PAL) oils with or without 1% tea polyphenols (TP) for 3 weeks, and chemical mediator releasing activity from rat peritoneal exudat e cells (PEC) was measured. Histamine releasing activity was not influenced by TP, while histamine release and intracellular histamine content were si gnificantly increased in the PAL-fed group. On the contrary, leukotriene B- 4 (LTB4) release was significantly lower in rats fed PER than in those fed SAF and PAL, and TP significantly decreased the release in all fat groups. TP also significantly inhibited the release of LTB4, which was generated on ly in rats fed PER. TP significantly decreased the proportion of arachidoni c acid (AA) in PEC in the SAF-fed group and that of eicosapentaenoic acid ( EPA), the precursor of LTB5 in the PER-fed group, but did not influence tha t of AA in the PAL- and PER-fed group. These results suggest that ingestion of TP improves type I allergic symptom through the inhibition of LT releas e though the inhibition by TP could not be totally explained by the reducti on of substrate fatty acid.