Changes of phospholipase D activity of rat peritoneal mast cells in degranulation.

AIM: To study the changes of phospholipase D (PLD) activity of actively sensitized rat peritoneal mast cells (RPMC) in degranulation. METHODS: Degranulation of RPMC was determined by measurement of beta-hexosaminidase release. PLD activity assay was carried out by measurement of PLD product, choline, with chemiluminescent oxidation of luminol. RESULTS: Actively sensitized RPMC challenged with ovalbumin (0.5-8 mg/L for 120 s, 4 mg/L for 15-120 s) resulted in significant activation of PLD accompanied with the increment of beta-hexosaminidase release. PLD activity of sensitized RPMC was increased by more than 2-fold compared with that of unsensitized RPMC which contained low levels of PLD activity [(35+/-13) pmol choline/min in 10(6)cells], but beta-hexosaminidase releases of the sensitized cells were as low as spontaneous releases. After challenge with ovalbumin 4 mg/L for 120 s, PLD activity of sensitized RPMC was increased to (155+/-43) pmol choline/min in 10(6)cells and beta-hexosaminidase release was also elevated significantly (4.5-fold of spontaneous release, n=6, P<0.05). When unsensitized RPMC were stimulated with antigen, PLD activity and beta-hexosaminidase release of the cells were hardly changed. Sensitized RPMC were treated with 1 % 1-butanol or 2,3- disphosphoglycerate 10 mmol/L before challenge with ovalbumin, these drugs induced an inhibition of PLD activity and a reduction of beta-hexosaminidase release to basal level. 1-Butanol 0.1 % also worked. CONCLUSION: Phospholipase D plays an important role in the regulation of beta-hexosaminidase release in actively sensitized rat peritoneal mast cells.

[Role of phospholipase D in priming of rat peripheral leukocytes by lipopolysaccharide and antigen].

OBJECTIVE: To 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. METHODS: The 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. RESULT: Compared 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.

[Cyclic nucleotides phosphodiesterase activity in a rat lung model of asthma]

OBJECTIVE: To assess the change of cGMP-PDE and cAMP-PDE activity in a rat lung model of asthma. METHODS: cGMP-PDE and cAMP-PDE activity were determined by HPLC. RESULTS: Both cAMP-PDE activity and cGMP-PDE activity in the lung tissue of antigen-challenged rats were higher than that from the normal rats (P <0.05). CONCLUSION: In the rat lung model of asthma, cyclic nucleotides phosphodiesterase activity was elevated. This may be significant in the pathogenesis of asthma.