Involvement of thiols in the induction of inward current induced by silver in frog skeletal muscle membrane

Effects of Nano-particles on Histo-pathological changes of the fish

Regarding fast development of the nanotechnology and the probably of it's side effects on aquatic body organs, this study investigate the effects of nanosilver administration on histology of gill, kidney and biochemical parameters in common carp. The silver nanoparticles were synthesized in a one-step reduction process in an aqueous solution. 60 O. mykiss were obtained from a local commercial hatchery. Fish were divided randomly into four groups. Control group was kept in dechlorinated tap water without any add-on material. Experimental groups were exposed to concentration of 3, 300 and 1000 mg/L of nanosilver solution for eight weeks, respectively. Biochemical analyses of sera, histological alterations of the gill and kidney tissue were done. Aneurism in the secondary lamellae and hyperplasia of epithelium in gills, adhesion of the gill lamellae, inducing hyaline cast formation, significant decreasing in the glomerular diameter and formation of intra cytoplasmic vacuoles in the various urinary tubules were seen in experimental groups. The serum levels of total protein was decreased significantly (P < 0.05) by increasing nanosilver concentration but ALP, LDH, AST and ALT increased significantly (P < 0.05). It is concluded that nanosilver induces gill and kidney damages and changes the biochemical parameters of O. mykiss juveniles in different concentrations.

Redox modulation of diaphragm contractility: Interaction between DHPR and RyR channels

Previous reports indicate that reactive oxygen species (ROS) may modulate contractility in skeletal muscle. Although Ca(2+)-sensitivity of the contractile apparatus appears to be a primary site of regulation, dihydropyridine receptor (DHPR or L-type Ca(2+) channels) and calcium efflux in isolated sarcoplasmic reticulum (SR) vesicles appear to be redox sensitive as well. However, DHPR as a target is poorly understood in intact muscles at body temperature, particularly in the diaphragm, a muscle more dependent on external Ca(2+) than locomotor muscles. Previously, we reported that oxidant challenge via xanthine oxidase (XO) alters the K(+) contractures in diaphragm fiber bundles, suggestive of a role of L-type Ca(2+) channels. Contractility of isolated rat diaphragm fiber bundles revealed a biphasic response to ROS challenge that was dose and time dependent. Potentiation of twitch and low-frequency diaphragm fiber bundle contractility with 0.02 U•ml(-1) XO was reversible or partially preventable with washout, dithiothreitol, and the SOD/catalase mimetic EUK-134. The RyR antagonist ruthenium red inhibited xanthine oxidase-induced potentiation, while the RyR agonist caffeine elevated diaphragm twitch and low-frequency tension in a non-additive manner by 55% when introduced simultaneously with ROS challenge. The DHPR antagonist nitrendipine (15 μM) inhibited elevation in low-frequency diaphragm tension produced by ROS challenge. Caffeine threshold tension curves were shifted to the left with 0.02 U•ml(-1) XO, but this effect was partially reversed with 15 μM nitrendipine. These results are consistent with the hypothesis that DHPR redox state and RyR function are modulated in an interactive manner, affecting contractility in intact diaphragm fiber bundles.

Accumulation of silver from drinking water into cerebellum and musculus soleus in mice

In spite of the general toxicity, ecotoxicity and sparsely known metabolism of silver, WHO allows silver ions (Ag) up to 0.1 mg/l in drinking water disinfection. In order to determine the accumulation and distribution of silver in a mammalian body, mice were given for 1 and 2 weeks drinking water containing a 3-fold lower concentration, namely 0.03 mg/l silver ions as silver nitrate labelled with 110mAg. The silver concentrations in different tissues were analysed by gamma radioactivity. The saturation of tissues with silver seems to occur quickly, as there were no statistical differences between silver contents of mice tissues in spite of the study design that mice were administered silver for 1 or 2 weeks. The highest concentrations were found in musculus soleus (m. soleus), cerebellum, spleen, duodenum, and myocardial muscle in the rank order. Concentrations of silver in musculus gastrocnemius (m. gastrocnemius) were found to correlate negatively with cerebrum and positively with blood and kidneys. The accumulation of silver into organs and tissues important in motor functions may be of relevance especially in emergency and catastrophe situations in which accurate motor functions may be critical. A re-evaluation of the present recommendations on the use of silver salts for disinfection of drinking water might be necessary.

A possible effect of sulfhydryl reagents on the contractile activity of the rat detrusor muscle

We aimed to investigate the effect of sulfhydryl (SH) inactivating agents, ethacrynic acid and N-ethylmaleimide, on the contractile activity of rat detrusor muscle. Wistar Kyoto rats weighing 150-250 g were anaesthetized with ketamine and bled to death. The urinary bladders were surgically removed and detrusor strips were mounted under 0.5 g tension in organ baths. The responses were recorded with isotonic transducers on polygraph paper. After an equilibrium period, the tissues were contracted by electrical field stimulation, acetylcholine, ethacrynic acid or N-ethylmaleimide and the effects of L-cysteine, glutathione, verapamil, Ca(2+)-free solution, sodium nitroprusside or atropine were then examined on these contractions. Verapamil, Ca(2+)-free solution or atropine significantly reduced the contractions elicited by electrical field stimulation and acetylcholine whereas L-cysteine, glutathione or sodium nitroprusside had no effect on the contractions in response to these stimuli. L-Cysteine, glutathione, verapamil or Ca(2+)-free solution significantly inhibited the contractions induced by ethacrynic acid or N-ethylmaleimide. Sodium nitroprusside slightly inhibited only the contraction induced by ethacrynic acid but not that with N-ethylmaleimide. Atropine has no action on the contractions in response to these SH reagents. These findings suggest that SH reagents may play a role in the contractile activity of rat detrusor muscle and this action seems to be related to the gating of Ca(2+) channels. Further experiments are needed to determine the cellular mechanism(s) of action by which these SH reagents act on the detrusor smooth muscle.

Modulation of the extracellular divalent cation-inhibited non-selective conductance in cardiac cells by metabolic inhibition and by oxidants

The effect of metabolic inhibition and oxidative stress on the monovalent cation-permeable, extracellular divalent cation-inhibited non-selective conductance was investigated in ventricular myocytes at 22 degrees C. Under whole-cell voltage-clamp, with L-type Ca2+ channels blocked by nifedipine, and K+ currents blocked by Cs+ substitution for K+, removal of Ca2+(o)and Mg2+(o) induced a non-selective current (I(NS-(Ca)o)) in mouse, rabbit and rat cells. Removal of glucose increased I(NS-(Ca)o)in the absence of Ca2+(o) and Mg2+(o), but failed to induce this current in the presence of the divalent cations. Further inhibition of glycolysis by 2-deoxyglucose (DOG; 10 mM, in zero glucose) or of mitochondrial function by rotenone (10 microM) or NaCN (5 mM) also failed to induce I(NS-(Ca)o)in the presence of Ca2+(o) and Mg2+(o). Even when given together, DOG and rotenone did not induce I(NS-(Ca)o) in the presence of divalent cations. Preactivated I(NS-(Ca)o) was increased by the oxidants thimerosal (50 microM), diamide (500 microM) and pCMPS (50 microM). However, none of these drugs nor NEM (1 mM) did elicit I(NS-(Ca)o)in the presence of Ca2+(o) and Mg2+(o). Exposure of rat myocytes to Ag+ induced a current resembling I(NS-(Ca)o) (reversing at -5 mV; blocked by 100 microM Gd3+) even in the presence of divalent cations. The data indicate that metabolic inhibition only regulates activated I(NS-(Ca)o)but does not induce the opening of closed channels, and that small oxidants like Ag+ may induce I(NS-(Ca)o) activation by accessing at sites unavailable for larger molecules.

Comparative studies on the induction of muscle contracture in mouse diaphragm and Ca2+ release from sarcoplasmic reticulum vesicles by organotin compounds

Effects of organotins, including triethyltin and tributyltin, on skeletal muscle were studied with diaphragm and isolated sarcoplasmic reticulum membrane vesicles. Triethyltin induced muscle contracture in mouse diaphragm while tributyltin had comparatively less potency and efficacy in inducing the muscle contracture. The contracture induced by tributyltin was inhibited when the diaphragm was pretreated with low Ca2+ medium or caffeine while the contracture induced by triethyltin persisted in the Ca2+-free medium but was inhibited by pretreatment of caffeine. Pretreatment of dithiothreitol blocked the contracture induced by tributyltin but not that by triethyltin. Triethyltin dose-dependently induced Ca2+ release from sarcoplasmic reticulum vesicles and inhibited the Ca2+-ATPase activity. These results suggested that triethyltin induced contracture in mouse diaphragm was mainly by induction of Ca2+ release and inhibition of Ca2+ uptake of the internal Ca2+ storage site the sarcoplasmic reticulum, while the tributyltin induced contracture might be due to enhancement of extracellular Ca2+ influx which further induce the release of internal Ca2+ through the Ca2+-induced Ca2+ release mechanism.