OBJECTIVETo investigate whether or not lipopolysaccharide (LPS) and ovalbumin (OA) prime rat peripheral leukocytes, the effect of sensitization on priming and the role of phospholipase D in priming.

METHODSThe peripheral leukocytes were separated and purified from sensitized or unsensitized rats. LPS or OA was used as a priming agent and formylmethionylphenylalanine (fMLP) as an activating agent. Degradation of leukocyte was determined by measurement of elastase release and myeloperoxidase (MPO) activity. Phospholipase D (PLD) activity was assayed by the generation of choline,which was measured by choline-oxidase-catalyzed formation of H(2)O(2) and Trinder reaction.

RESULTCompared with cells treated by fMLP alone,leukocytes from unsensitized rat challenged with fMLP after incubated with LPS released more elastase and MPO (P<0.05). But there was no significant difference between leukocytes challenged with fMLP after incubated with OA and fMLP treated alone. In sensitized rat,there was no difference between leukocytes challenged with fMLP after incubated with LPS and fMLP treated alone. But leukocytes challenged with fMLP after incubated with OA released significantly more elastase and MPO than fMLP treated alone (P<0.05). A significant correlation was obtained between the release of elastase and PLD activity (r(s)=0.51,P<0.01), and also between the release of MPO and PLD activity (r(s)=0.73,P<0.01) in unsensitized rat. In sensitized rat, it was 0.48 (P<0.01) and 0.37 (P<0.05) respectively.

CONCLUSION(1) LPS primes peripheral leukocytes from unsensitized rats; (2) OA primes peripheral leukocytes from actively sensitized rats; (3) PLD plays a role in priming of rat peripheral leukocytes.