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Pasteurization and storage affect nonenzymatic and enzymatic antioxidative agents in human milk. It appears that nonenzymatic antioxidative systems in colostrum and milk are different. The effects of processing may be partially compensated by fortification/spiking with ascorbate before use.

Background and purpose:The effects of hydrogen peroxide (H2O2) on uterine smooth muscle are not well studied. We have investigated the effect and the mechanism of action of exogenous hydrogen peroxide on rat uteri contractile activity [spontaneous and calcium ion (Ca 2+ )-induced] and the effect of such treatment on anti-oxidative enzyme activities. Experimental approach: Uteri were isolated from virgin Wistar rats and suspended in an organ bath. Uteri were allowed to contract spontaneously or in the presence of Ca 2+ (6 mM) and treated with H2O2 (2 mM-3 mM) over 2 h. Anti-oxidative enzyme activities (manganese superoxide dismutase-MnSOD, copper-zinc superoxide dismutase-CuZnSOD, catalase-CAT, glutathione peroxidase-GSHPx and glutathione reductase-GR) in H2O2-treated uteri were compared with those in uteri immediately frozen after isolation or undergoing spontaneous or Ca 2+ -induced contractions, without treatment with H2O2. The effect of inhibitors (propranolol, methylene blue, L-NAME, tetraethylamonium, glibenclamide and 4-aminopyridine) on H2O2-mediated relaxation was explored. Key results: H2O2 caused concentration-dependent relaxation of both spontaneous and Ca 2+ -induced uterine contractions. After H2O2 treatment, GSHPx and MnSOD activities were increased, while CuZnSOD and GR (In Ca 2+ -induced rat uteri) were decreased. N w -nitro-L-arginine methyl ester antagonized the effect of H2O2 on Ca 2+ -induced contractions. H2O2-induced relaxation was not affected by propranolol, potentiated by methylene blue and antagonized by tetraethylamonium, 4-aminopyridine and glibenclamide, with the last compound being the least effective. Conclusions and implications: H2O2 induced dose-dependent relaxation of isolated rat uteri mainly via changes in voltagedependent potassium channels. Decreasing generation of reactive oxygen species by stimulation of anti-oxidative pathways may lead to new approaches to the management of dysfunctional uteri.

Changes in erythrocyte ADE activities suggest that oxidative stress, involved in the motor neurone pathogenesis of SALS and FALS, also has systemic effects. Differences in ADE systems between the study groups revealed the presence of different types of oxidative pressure, indicating the potential additional benefit of individually designed anti-oxidant cocktail therapies.

Recent findings indicate that nitric oxide (NO*) over-production might be an important factor in the pathogenesis of sporadic amyotrophic lateral sclerosis (SALS). We measured significantly higher concentrations of uric acid and thiol group-containing molecules (R-SH groups) in the cerebrospinal fluid (CSF) from SALS patients compared to controls. The above factors, together with a slightly increased free iron concentration found in the CSF, favour conditions necessary for the formation of the dinitrosyl iron complex, capable of NO* bio-transformation. Thus, we performed ex vivo saturation of CSF (from both SALS patients and controls) with NO*. A decrease in the level of R-SH was found. This was more pronounced in the CSF from SALS patients. In the CSF from SALS patients the production of nitrite and hydroxylamine was greater than that observed in the CSF from controls. Moreover, we also found increased Cu,Zn-SOD activity in the CSF from SALS patients (when compared to control subjects) but no activity corresponding to Mn-SOD in any CSF samples. As Cu,Zn-SOD can react with nitroxyl forming NO*, the conditions for a closed, but continuous, loop of NO* biotransformation are present in the CSF of ALS patients.

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Kratak sadr`aj: Produkcija slobodnih radikala u eritrocitima uglavnom se odnosi na nastajanje superoksid anjon radikala (O 2 .-) putem autooksidacije oksihemoglobina u methemoglobin. Ljudski eritrociti izlo`eni su prooksidacionom delovanju vodonik-peroksida nastalog dismutacijom O 2 .-ili iz cirkulacije, kao i azot oksidu (NO) iz cirkulacije. Od di rektnih reakcija slobodnih radikala, reakcija O 2 .-i NO uz nastajanje peroksinitrita je reakcija sa primarno {tetnim posledicama po eritrocite. U eritrocitima se nalaze enzimi za{tite od oksidacionih o{te}enja, kao {to su superoksid dismu taza (SOD, EC 1.15.1.1), katalaza (CAT, EC 1.11.1.6), glutation peroksidaza (GSHPx, EC 1.11.1.9) i glutation reduktaza (GR, EC 1.6.4.2) kao i komponente male mo lekulske mase (glutation, vitamini E i C). Njihovim sadej stvom se kanali{u reakcije slobodnih radikala tako da di rektna o{te -}enja biomakromolekula budu {to manja. Me|u tim, kako nema de novo sinteze enzima u maturiranim eri trocitima, kapacitet ovih sistema je ograni~en, jer slobo d noradikalske vrste i direktno inhibiraju neke od enzima. Promene na enzimima i njihova inhibicija slobodnim radi kalima uti~u na kapacitet za{tite od oksidacionih o{te}enja i relativni udeo pojedinih komponenti u ukupnom antioksi da tivnom poten cijalu. To se mo`e pratiti i preko promena aktiv nosti pojedina~nih komponenti, ali i me |u sobnih odnosa izme|u komponenti antioksidativne odbrane diskrimina cio nim sta ti sti ~kim metodama, koje ukazuju na sveukupnost i kompleksnost odnosa antioksida tivnih kompo nenti u eritro citima i njihov sistemski zna~aj.

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