Oxidative stress inactivates ecto-5'-nucleotidase by inhibiting protein kinase C in rat hearts in vivo.

Examined in the present study, allopurinol are xanthine oxidase inhibitors for use in rat hearts in vivo dialysis technology and ventricular myocardial intersitial adenosine production can increase. The microdialysis probe was implanted in the left ventricular myocardium of anesthetized rat hearts and the tissue in the vicinity of the dialysis was perfused with Tyrode's solution containing adenosine 5'-monophosphate (AMP) through the dialysis probe at a rate of 1.0ml/min to assess the activity of ecto-5'-nucleotidase. Allopurinol (10µM) significantly increased the level of adenosine in rat heart dialysate (n=6, p<0.05), which was inhibited by chelerythrine, 10µM, an antagonist of protein kinase C (PKC). Another free radical scavenger, coenzyme Q10 (CoQ10, 100µM) or ascorbic acid (Vitamin C; 100µM) also increased adenosine production. In addition, allopurinol enhanced the diacylglycerol (DAG; 50µM)-induced also increases in adenosine production by 71.5±12.0% (n=6, P<0.05), to a level significantly (P<0.05) greater than the increase caused by DAG alone (33.0±10.6%). In the presence of allopurinol (10µM), a marked elevation of AMP-primed dialysate adenosine in ischemia/reperfused rat hearts was observed. Free radical generation may suppress adenosine production via activation of PKC. The results suggest that oxidative stress may cause inactivation of nucleotidase, adenosine production in rat heart.

Opening of ATP-sensitive K(+) (KATP) channels enhance hydroxyl radical generation induced by MPP(+) in rat striatum.

The present study examined whether opening of adenosine triphosphate (ATP) sensitive K(+) (KATP) channels can enhance 1-methyl-4-phenylpyridinium (MPP(+))-induced hydroxyl radical (OH) generation in rat striatum. Rats were anesthetized, and sodium salicylate in Ringer's solution (0.5nmol/ml per min) was infused through a microdialysis probe to detect the generation of OH as reflected by the non-enzymatic formation of 2.3-dihydroxybenzoic acid (DHBA) in the striatum. MPP(+) (5mM) enhanced generation of OH with concomitant increased efflux of dopamine (DA). Cromakalim (100µM), a KATP channel opener, through the microdialysis probe significantly increased both DA efflux and OH formation induced by MPP(+). Another KATP channel opener, nicorandil (1mM), also increased the level DA or DHBA, but these changes were not significant. However, in the presence of glibenclamide (10µM), a KATP channel antagonist, and the increase of MPP(+)-induced DA or DHBA were not observed. Cromakalim (10, 50 and 100µM) increased MPP(+)-induced DHBA formation in a concentration-dependent manner. However, the effects of cromakalim in the presence of glibenclamide were abolished. These results suggest that opening of KATP channels may cause OH generation by MPP(+).

Evidence for existence of thyroid hormone inducible semicarbazide-sensitive amine oxidase (SSAO) in rat heart cytosol.

BACKGROUND: Semicarbazide-sensitive amine oxidase (SSAO; EC; 1.4.3.6.) has widespread tissue distribution, and the physiological role of SSAO is quite well known through its involvement in several pathological states. AIMS: The present study examined modulators of SSAO which might be present in the rat heart cytosol and looked for changes in SSAO modulatory activity. METHODS: An endogenous inhibitor of SSAO was separated by gel filtration from 105,000g supernate of T4-treated rat heart cytosol. SSAO inhibition fraction was referred to as "endogenous SSAO inhibitor". RESULTS: The inhibition by this inhibitor was concentration-dependent. Inhibition of SSAO was not enhanced by varying the time of preincubation of the enzyme, indicating reversible inhibition of SSAO. The molecular weight of this inhibitor was estimated to be 1000-1100 by gel filtration. The isoelectric point (pI) value was determined to be 4.8 isoelectric focusing. This inhibitor was found to be heat-stable and resistant to protease treatment. SSAO inhibition activity was much lower in the cytosol of thyroidectomized, non-T4-treated rats than T4-treated rats, suggesting that this inhibitor was induced by thyroid hormone T4. SSAO activity in rat heart might be regulated by the level of this inhibitor. CONCLUSION: These results suggest the presence of SSAO inhibitor in T4-treated rat cytosol and that the level of this inhibitor is regulated by thyroid hormone.

Fluvastatin, an HMG-CoA reductase inhibitor, facilitate adenosine production in the rat hearts via activation of ecto-5'-nucleotidase.

OBJECTIVE: The present study was examined whether fluvastatin, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, can increase the production of interstitial adenosine via activation of ecto-5'-nucleotidase in the ventricular myocardium, with use of microdialysis techniques in in situ rat hearts. METHODS: Adenosine in the dialysate collected during perfusion with Tyrode's solution containing 100µM AMP (through the probe) originated from the hydrolysis of AMP catalyzed by endogenous ecto-5'-nucleotidase, so that the level of adenosine reflected the activity of ecto-5'-nucleotidase in this tissue. RESULTS: Fluvastatin (100µM), an inhibitor of low-density lipoprotein (LDL) oxidation, significantly increased the concentration of adenosine measured in the presence of 100µM AMP (i.e., the activity of ecto-5'-nucleotidase) by 154.7±16.0% (n=6, P<0.05), an increase which inhibited an antagonist of the α1-adrenoceptor (prazosin, 50µM) or of protein kinase C (PKC; chelerythrine, 10µM). Fluvastatin (10-500µM) increased the level of AMP-primed dialysate adenosine in a concentration-dependent manner. CONCLUSION: These results indicate that fluvastatin increases in adenosine concentrations in the dialysate which resulted from activation of PKC, mediated by stimulation of α1-adrenoceptors, through activation of ecto-5'-nucleotidase.

Phytic acid suppresses ischemia-induced hydroxyl radical generation in rat myocardium.

The present study examined whether ischemia-reperfusion-induced hydroxyl radical (·OH) generation was attenuated by myo-inositol hexaphosphoric acid (phytic acid). A flexibly mounted microdialysis technique was used to detect the generation of ·OH in in vivo rat hearts. To measure the level of ·OH, sodium salicylate in Ringer's solution (0.5mM or 0.5 nmol/µl/min) was infused directly through a microdialysis probe to detect the generation of ·OH as reflected by the nonenzymatic formation of 2,3-dihydroxybenzoic acid (2,3-DHBA). To confirm the generation of ·OH by Fenton-type reaction, iron(II) was infused through a microdialysis probe. A positive linear correlation between iron(II) and the formation of 2,3-DHBA (R(2)=0.983) was observed. However, the level of 2,3-DHBA in norepinephrine (100 µM) plus phytic acid (100 µM) treated group were significantly lower than those observed in norepinephrine-only-treated group (n=6, *p<0.05). To examine the effect of phytic acid on ischemia-reperfusion-induced ·OH generation, the heart was subjected to myocardial ischemia for 15 min by occlusion of the left anterior descending coronary artery (LAD). When the heart was reperfused, the normal elevation of 2,3-DHBA in the heart dialysate was not observed in animals pretreated with phytic acid. These results suggest that phytic acid is associated with antioxidant effect due to the suppression of iron-induced ·OH generation.

A suggestion for the role of infertile woman and support.

Data were collected in semi-structured interviews with four women who have experienced infertility treatments and the results were analyzed based on their expressed feelings, particularly the support they demanded from their nursing attendants. We came to five conclusions: Feeling imperfect; Feeling the pressure of achievement from their families and future; Infertility treatments have no guarantees and the medical attendants are also uncertain; They feel that they undergo infertility treatments alone but the support of a fellow patient helps them; Infertility treatments have an age limit so the patients worry about time.