Michiko Inoue

Enhancing and inhibitory effects of nitric oxide on superoxide anion generation in human polymorphonuclear leukocytes

1 The effects of sodium nitroprusside (SNP, a nitric oxide donor) and authentic nitric oxide (NO) on superoxide anion (O2−) generation were investigated in human polymorphonuclear leukocytes (PMNs). 2 Neither SNP (10 nM to 10 4μm) nor NO (40 nM to 40 μm) alone induced O2− generation or change of intracellular Ca2+ concentration ([Ca2+]i) in human PMNs. 3 Pretreatment with SNP or NO at the concentrations used (SNP, 10 nM to 10 μm: NO, 40 nM to 40 μm) showed a biphasic concentration‐dependent effect on O2− generation induced by f‐methionyl‐leucyl‐phenylalanine (FMLP). Low concentrations of SNP (10 nM to 100 nM) and NO (400 nM) did not affect either basal cyclic GMP levels or cyclic GMP levels stimulated by FMLP, but enhanced FMLP‐induced O2− generation and [Ca2+]i elevation. On the other hand, high concentrations of SNP (10 μm) and NO (40 μm) alone elevated cyclic GMP levels and inhibited FMLP‐induced O2− generation and [Ca2+]i elevation. 48 ‐Bromo‐cyclic GMP (8‐Br‐cyclic GMP) at concentrations ranging from 1 μm to 1 mM did not induce O2− generation on its own and had little effect on FMLP‐induced O2− generation and [Ca2+]i elevation. 5 Addition of a high concentration of NO (40 μm) decreased authentic O2− formation by pyrogallol in a cell‐free system, but a low concentration of NO (400 nM) had no effect on this. On the other hand, addition of SNP in the concentration‐ranges used had no effect on authentic O2− formation by pyrogallol. 6 In this study, we have shown that SNP and NO have dual effects (enhancement and inhibition) on O2− generation induced by FMLP in human peripheral PMNs. The results suggest that the enhancement observed with SNP and NO at low concentrations is not mediated by activation of the guanylate cyclase‐cyclic GMP pathway. The suppressive effect of SNP and NO at higher concentrations is mediated by the NO‐induced O2−‐scavenging effect and activation of the guanylate cyclase‐cyclic GMP pathway.

Enzymic determination of serum oxalate

A new colorimetric, enzymic method for determination of serum oxalate is described using oxalate oxidase from barley seedlings. This method, based on a specific reaction of oxalate with oxidase is rapid, simple and precise. The percentage recoveries of oxalate added to serum ranged from 91.5 to 103. The oxalate content in the serum obtained from 50 healthy non-fasting donors varied from 0.06 mg/dl to 0.41 mg/dl. The proposed method showed a good correlation with a chemical method.

Potentiating effect of nicorandil, an antianginal agent, on relaxation induced by isoproterenol in isolated rat aorta : involvement of cyclic GMP-inhibitable cyclic AMP phosphodiesterase

Summary In rat aortic rings, isoproterenol (ISO) 109-3 × 10-6M relaxed the contraction induced by phenylephrine (PE) 3 × 10 7M. Pretreatment with nicorandil 3 × 10-7 and 3 × 10-7M potentiated the relaxation induced by ISO. Nicorandil 3 × 10 6M also potentiated the relaxations induced by forskolin 3 × 10 9-10 6M and dibutylyl-cyclic AMP 3 × 10-6-3 × 10 -4M. Nitroglycerin (NTG) 10 8M, but not cromakalim 3 × 10-8M, also potentiated the ISO relaxation. Pretreatment with glyburide 10 -6M or apamin 10-6M did not affect the potentiating action of nicorandil 3 × 10 -6M. Pretreatment with methylene blue (MB) 10 6M, but not with NG-monomethyl-L-arginine (NMMA), however, markedly inhibited the potentiating effect of nicorandil. Removal of endothelium impaired the relaxation induced by ISO but did not inhibit the potentiating effect of nicorandil. In addition, in the presence of MCI-154 (10-7M), which itself potentiated ISO-induced relaxation, nicorandil 3 × 10 6M did not further potentiate the relaxing response to ISO. Furthermore, nicorandil 3 × 10 -6M potentiated the increase in the tissue level of cyclic AMP caused by ISO 3 × 10-7M, whereas the nicorandil-induced increase in cyclic GMP levels were not affected by ISO. These results suggest that the potentiating effect of nicorandil on the relaxation induced by ISO is most likely due to inhibition of phosphodiesterase III (PDE III) by increased cyclic GMP levels.

Effect of mammalian lignans on f MLP‐induced oxidative bursts in human polymorphonuclear leucocytes

Abstract— We examined the effects of mammalian lignans, enterolactone, prestegane B and 2,3‐dibenzylbutane‐1,4‐diol (DBB) on superoxide production and luminol‐dependent chemiluminescence (LCL) response in human polymorphonuclear leucocytes (PMNs). The three lignans had no direct effect on the responses of human PMNs. DBB and prestegane B enhanced the superoxide production and LCL response induced by formylmethionyl‐leucyl‐phenyl‐alanine (f MLP), but enterolactone inhibited f MLP‐induced effects. The effects of DBB were stronger than those of prestegane B and the effects of DBB were inhibited by bromophenacyl bromide, mepacrine, N‐(6‐aminophenyl)‐5‐chloro‐t‐naphthalene sulphonamide and trifluoroperazine, but not by gossypol, nordihydroguaretic acid, indomethacin, staurosporine, 1‐(5‐isoquinolinesulphonyl)‐2‐methylpiperazine dihydrochloride or (R,S)‐2‐methoxy‐3‐(octadecyl‐car‐bamoyloxy)‐propyl‐2‐(2‐thiazolio)‐ethylphosphate. These results suggest that DBB primes the responses of human PMNs, and the priming effect is caused by the activation of phospholipase A2—and Ca2+ ‐calmodulin‐pathways, but not by the activation of lipoxygenase, cyclo‐oxygenase and protein kinase C or by the release of platelet activating factor.

Priming effect of 2,3-dibenzylbutane-1,4-diol (mammalian lignan) on superoxide production in human neutrophils

We investigated the effect of 2,3-dibenzylbutane-1,4-diol (DBB), a mammalian lignan, on superoxide production and [Ca2+]i mobilization in human neutrophils. DBB did not generate superoxide production by itself, but enhanced the FMLP or A23187-induced superoxide production in a dose dependent manner. DBB did not influence the OAG-induced superoxide production. The priming effect of DBB was inhibited by W-7 or trifluoroperazine, but not by H-7 or staurosporine. And the priming effect of DBB was observed in the presence or absence of extracellular Ca2+. DBB enhanced the low dose FMLP-induced [Ca2+]i mobilization. These results suggest that the priming effect of DBB in human neutrophils may be caused by the activation of the calcium-calmodulin pathway but not the protein kinase pathway.

Sex-related difference in the effect of aspirin on prostaglandin metabolism in rat platelet and aorta

Abstract The effect of aspirin on the production of the arterial prostacyclin (PGI2)-like substance and platelet malondialdehyde (MDA) was investigated in rats of both sexes. No significant sex difference observed with the arterial PGI2-like substance. But, following the aspirin treatment, the production of the PGI2-like substance was significantly decreased in male rats. There was significant sex difference in the production of platelet MDA before the aspirin treatment. And after the aspirin treatment, platelets of both sexes produced significantly less MDA. It is possible that sex difference in the effect of aspirin is related to the quantitative difference of cyclooxygenase activity between platelets and vasal wall.