8 research outputs found
Reversible Oxidation of Myometrial Voltage-Gated Potassium Channels with Hydrogen Peroxide
The uteri, spontaneously active or Ca2+ (6 mM) induced, were allowed to equilibrate, and to inhibit voltage-gated potassium () channels 1 mM 4-amino pyridine (4-AP) was applied for 15 min before adding H2O2 .  H2O2 was added cumulatively: 2 μM, 20 μM, 200 μM, 400 μM, and 3 mM. Average time for H2O2 concentrations (2, 20, 200, and 400) μM to reach its full effect was 15 min. H2O2 3 mM had a prolonged effect and therefore was left to act for 30 min. Two-way ANOVA showed significant differences in time dependency between spontaneous and Ca2+-induced rat uteri after applying 3 mM H2O2 (type of contraction, ), but not 400 μM H2O2 (). Our results indicate that H2O2 oxidises channel intracellular thiol groups and activates the channel, inducing relaxation. Cell antioxidative defence system quickly activates glutathione peroxidase (GSHPx) defence mechanism but not catalase (CAT) defence mechanism. Intracellular redox mechanisms repair the oxidised sites and again establish deactivation of channels, recuperating contractility. In conclusion, our results demonstrate that channels can be altered in a time-dependent manner by reversible redox-dependent intracellular alterations
The effects of wild-type and mutant SOD1 on smooth muscle contraction
In this work we compared the mutated liver copper zinc-containing superoxide dismutase (SOD1) protein G93A of the transgenic rat model of familial amyotrophic lateral sclerosis (FALS), to wild-type (WT) rat SOD1. We examined their enzymatic activities and effects on isometric contractions of uteri of healthy virgin rats. G93A SOD1 showed a slightly higher activity than WT SOD1 and, in contrast to WT SOD1, G93A SOD1 did not induce smooth muscle relaxation. This result indicates that effects on smooth muscles are not related to SOD1 enzyme activity and suggest that heterodimers of G93A SOD1 form an ion-conducting pore that diminishes the relaxatory effects of SOD1. We propose that this type of pathogenic feedback affects neurons in FALS
Chloride channels mediate sodium sulphide-induced relaxation in rat uteri
Background and PurposeHydrogen sulphide reduces uterine contractility
and is of potential interest as a treatment for uterine disorders. The
aim of this study was to explore the mechanism of sodium sulphide
(Na2S)-induced relaxation of rat uterus, investigate the importance of
redox effects and ion channel-mediated mechanisms, and any interactions
between these two mechanisms.
Experimental ApproachOrgan bath studies were employed to assess the
pharmacological effects of Na2S in uterine strips by exposing them to
Na2S with or without Cl- channel blockers (DIDS, NFA, IAA-94,
T16Ainh-A01, TA), raised KCl (15 and 75mM), K+ channel inhibitors
(glibenclamide, TEA, 4-AP), L-type Ca2+ channel activator (S-Bay K
8644), propranolol and methylene blue. The activities of antioxidant
enzymes were measured in homogenates of treated uteri. The expression of
bestrophin channel 1 (BEST-1) was determined by Western blotting and
RT-PCR.
Key ResultsNa(2)S caused concentration-dependent reversible relaxation
of spontaneously active and calcium-treated uteri, affecting both
amplitude and frequency of contractions. Uteri exposed to 75mM KCl were
less sensitive to Na2S compared with uteri in 15mM KCl. Na2S-induced
relaxations were abolished by DIDS, but unaffected by other modulators
or by the absence of extracellular HCO3-, suggesting the involvement of
chloride ion channels. Na2S in combination with different modulators
provoked specific changes in the anti-oxidant profiles of uteri. The
expression of BEST-1, both mRNA and protein, was demonstrated in rat
uteri.
Conclusions and ImplicationsThe relaxant effects of Na2S in rat uteri
are mediated mainly via a DIDS-sensitive Cl--pathway. Components of the
relaxation are redox- and Ca2+-dependent
Differences in direct pharmacologic effects and antioxidative properties of mature breast milk and infant formulas
Objective: Early-onset and exclusive breast-feeding provides a significant health benefit to infants compared with infant formulas. The aim of this study was to compare mature breast milk with standard infant formulas by examining their effects on non-vascular smooth muscle contraction and their antioxidative properties. Methods: The pharmacologic effects of breast milk and formulas were examined using a model system of the rat uterine smooth muscle contraction. Electron paramagnetic resonance spin-trapping spectroscopy was used to compare the antioxidative capacities of breast milk (obtained in the ninth week of lactation) with commercial infant formulas against hydroxyl radical production in the Fenton reaction. The activities of superoxide dismutase, glutathione peroxidase, and the sulfhydryl group were determined in the breast milk and infant formulas. Results: In contrast to the infant formulas, breast milk exerted a relaxing effect on isolated non-vascular smooth muscle. In general, breast milk showed higher antioxidative activity compared with the infant formulas. In all samples, the generation of hydroxyl radicals led to the formation of carbon-centered and ascorbyl radicals. Conclusions: Human milk exerts direct pharmacologic relaxation effects and provides better antioxidant protection compared with infant formulas because of the presence of specific enzymatic components, such as human superoxide dismutase. We propose that these effects should be advantageous to an infant's gastrointestinal tract by supporting the normal work of the smooth musculature and maintaining redox homeostasis and may represent one of the mechanisms by which breast-feeding benefits health
Influence of absorbed radiation dose following computed tomography on the antioxidative status in rabbit testicles
© 2018 by the Serbian Biological Society. In recent years, computed tomography (CT) has become very common in veterinary medicine. It is well known that testicles are organs with high radiosensitivity and their function can be impaired even after exposure to low radiation doses. In this work, we calculated the absorbed radiation doses after CT was performed with different voltage/current levels and correlated it with the activity of antioxidant enzymes in rabbit testicles. Two hours after CT, the activities of catalase (CAT) and glutathione peroxidase (GSH-Px) were increased in the testicles of animals that received an absorbed dose of 29.2 mGy. The same changes, along with elevated glutathione reductase (GR) activity, were observed after 7 days in animals that received the highest absorbed dose (46.3 mGy). It would appear that absorbed doses above 27.8 mGy provoked the antioxidant reaction but the time scale of the reaction was dose-dependent. Examination of the obtained results revealed that the main denominator of CT influence was a higher current. Our results suggest that CT influences the antioxidant status in rabbit testicles. The changes in antioxidant enzyme activities were dose- and time-dependent and influenced by the applied current
Beyond H<sub>2</sub>S and NO Interplay: Hydrogen Sulfide and Nitroprusside React Directly to Give Nitroxyl (HNO). A New Pharmacological Source of HNO
Hydrogen sulfide (H<sub>2</sub>S) has been increasingly
recognized as an important signaling molecule that regulates both
blood pressure and neuronal activity. Attention has been drawn to
its interactions with another gasotransmitter, nitric oxide (NO).
Here, we provide evidence that the physiological effects observed
upon the application of sodium nitroprusside (SNP) and H<sub>2</sub>S can be ascribed to the generation of nitroxyl (HNO), which is a
direct product of the reaction between SNP and H<sub>2</sub>S, not
a consequence of released NO subsequently reacting with H<sub>2</sub>S. Intracellular HNO formation has been confirmed, and the subsequent
release of calcitonin gene-related peptide from a mouse heart has
been demonstrated. Unlike with other thiols, SNP reacts with H<sub>2</sub>S in the same way as rhodanese, i.e., the cyanide transforms
into a thiocyanate. These findings shed new light on how H<sub>2</sub>S is understood to interact with nitroprusside. Additionally, they
offer a new and convenient pharmacological source of HNO for therapeutic
purposes