Effects of oxidizing and reducing agents on ovine pulmonary artery responses to nitric oxide donors, sodium nitroprusside and 3-morpholino-sydnonimine.

Nitrovasodilators-sodium nitroprusside (SNP; 10(-9)-10(-4) M) and 3-morpholino-sydnonimine (SIN-1; 10(-9)-10(-4) M) produced concentration-dependent relaxation of the fourth generation sheep pulmonary artery, preconstricted with 5-hydroxytryptamine (1 microM). Oxidizing agents [oxidized glutathione (GSSG, 1 mM) and CuSO4 (5 and 20 microM)] and reducing agents [dithiothreitol (DTT, 0.1 mM), ascorbic acid (1 mM) and reduced glutathione (GSH, 1 mM)] caused opposite effects on nitric oxide (NO)-induced vasodilation in the artery. Ascorbic acid and GSH potentiated the NO responses, while GSSG and CuSO4 inhibited relaxation caused by the nitrovasodilators. DTT, however, reduced the relaxant potency and efficacy of SNP and SIN-1. Pretreatment of the pulmonary artery strips with DTT (0.1 mM) inhibited SNP (10 microM)-induced Na(+)-K(+)-ATPase activity, while ascorbic acid (1 mM) and GSH (1 mM) had no effect either on basal or SNP (10 microM)-stimulated 86Rb uptake, an index of Na(+)-K(+)-ATPase activity, in ovine pulmonary artery. The results suggest that reducing agents like ascorbic acid may have beneficial effect in improving the vascular function under oxidative stress.

Cytogenetic effects of a mixture of selected metals following subchronic exposure through drinking water in male rats.

The current study examines the genotoxic effects of subchronic exposure via drinking water to a mixture of eight metals (arsenic, cadmium, lead, mercury, chromium, nickel, manganese and iron) found as contaminants of water sources in different parts of India and its possible association with oxidative stress. Male rats were exposed to the mixture at 0, 1, 10 and 100 times the mode concentration of each metal daily for 90 days. Another dose group at concentration equivalent to maximum permissible limit (MPL) for each metal and a reference group given ip cyclophosphamide were incorporated. The mixture at 100x level significantly increased chromosomal aberrations and micronuclei induction (2.4 folds) in bone marrow cells and reduced the ratio of polychromatic to normochromatic erythrocytes by 25%. The mixture significantly increased sister chromatid exchange in bone marrow (1.67 and 2.3 folds) and spleen (1.57 and 1.98 folds) cells with both 10x and 100x doses. Cyclophosphamide was more potent than the mixture in causing cytogenetic damage in these parameters. In rat spleen, the mixture at 10x and 100x doses caused dose-dependent increase in lipid peroxidation (25.95 and 52.71%) and decrease in the activities of superoxide dismutase (20.36 and 40.62%), catalase (18.24 and 35.50%), glutathione peroxidase (22.33 and 36.12%) and glutathione reductase (19.22 and 31.35%) and in the level of GSH (19.76 and 35.15%). The results suggest that the mixture induced genotoxicity in rat bone marrow and spleen cells at concentrations relatively higher than that found in groundwater sources and the genotoxic effect could relate to induction of oxidative stress. However, observations with lower doses indicate that additive or synergistic interactions following exposure to metal components at MPL levels or at mode concentrations of contemporary groundwater levels in India may not result in clastogenicity in male rats.

Effects of calcium channel blocker, mibefradil, and potassium channel opener, pinacidil, on the contractile response of mid-pregnant goat myometrium.

The present study was undertaken to investigate the in vitro influence of mibefradil, a calcium channel blocker, and pinacidil, a potassium channel opener, on pregnant goat myometrial spontaneous rhythmic contractility and contractions induced with the agonist, oxytocin. Longitudinal strips from the distal region of uterus, collected from goats at midgestation, were mounted in an organ bath for recording isometric contractions. Mibefradil (10(-8)-10(-4) M) or pinacidil (10(-10)-10(-4) M), added cumulatively to the bath at an increment of 1 log unit, caused concentration-dependent inhibition of the spontaneous rhythmic contractions of isolated uterine strips. The rhythmic contraction was, respectively, abolished at 100 and 10 microM concentrations of mibefradil and pinacidil. In a concentration-dependent manner, mibefradil (1 and 10 microM) antagonized the contractions elicited with oxytocin (10(-5)-10(-2) IU). Pretreatment of uterine strips with glibenclamide (10 microM), a selective KATP channel blocker, caused a rightward shift of the concentration-response curve of pinacidil with a concomitant decrease in its pD2 value. Pinacidil (0.3, 1 and 3 microM), in a concentration-related manner, antagonized the oxytocin (10(-5)-10(-2) IU)-induced contractile response. The inhibition of spontaneous rhythmic contractions and antagonism of oxytocin-induced contraction by mibefradil in the pregnant goat myometrium may be related to the antagonism of voltage-dependent Ca2+ channels, while by pinacidil suggests that KATP channel could be a therapeutic target for tocolysis.

Subacute toxicity of anilofos, a new organophosphorus herbicide in male rats: effect on lipid peroxidation and ATPase activity.

Effects of anilofos on lipid peroxidation--an index of oxidative stress, ATPase activity--an integral part of active transport mechanisms for cations, GSH level and GST activity were evaluated in blood (erythrocyte/plasma), brain and liver of male rats after daily oral exposure to 50, 100 or 200 mg/kg for 28 days. None of the doses increased lipid peroxidation. The lowest dose, rather, produced marginally significant decrease in peroxidation in liver. Different doses of anilofos decreased GSH content and activities of GST and ATPases. Inhibition of total ATPase (34-44%) and Na+-K+-ATPase (45-52%) activities was maximum in liver, while that of Mg2+-ATPase (46-56%) was more in erythrocyte. Results indicate that anilofos may not cause oxidative damage to cell membrane in repeatedly exposed animals and may cause neuronal/cellular dysfunction by affecting ionic transport across cell membrane.

Subacute toxicity of anilofos, a new organophosphorus herbicide, in male rats: effect on some physical attributes and acetylcholinesterase activity.

In acute toxicity study, rats showed dose-dependent signs of cholinergic hyperactivity and behavioural alterations. Maximum intensity of symptoms was not associated with mortality. Oral LD50 was 1681 mg/kg. In subacute toxicity study, rats were orally administered 50, 100 or 200 mg/kg of anilofos once daily for 28 days. Signs and symptoms were observed mainly with 200mg/kg. At this dose, anilofos induced hypothermia and progressive weight loss. None of the anilofos-treated rats died. Weight of brain, lung, testis was not altered, while of liver, heart, spleen and kidney increased. Anilofos inhibited cholinesterase (ChE) activities of erythrocyte (41-67%), plasma (36%), blood (37-64%), brain (63-73%) and liver (28-48%). Total protein was decreased in plasma and liver. Results indicate moderate toxic potential of anilofos in mammals, substantial contribution of CNS-mediated effects in causing anilofos toxicity and no direct relationship between hypothermia and level of ChE inhibition.

Effect of isoproturon on male reproductive system: clinical, histological and histoenzyonological studies in rats.

Isoproturon, a nonhalogenated substituted phenylurea herbicide, was evaluated for its cumulative toxic effects on testicular histomorphology., steroid hormone biosynthesis-related enzymes, spermatogenesis and sperm cells in adult albino rats. The compound, suspended in refined groundnut oil, was administered (po) to rats for 10 weeks @ 0,200, 400 and 800 mg/kg/day for 6 days/week. Isoproturon, at 800 mg/kg dose, decreased epididymal sperm count and percentage of motile sperms and increased the percentage of morphologically abnormal sperm cells. At the same dose, diameter of seminiferous tubules was reduced, number of tubules per microscopic field was increased and the percentage of tubules with evidence of spermatogenesis decreased. However, the percentage of damaged tubules was increased with 400 and 800 mg/kg doses. Histoenzymological observations revealed dose-related reduction in the activities of glucose-6-phosphate dehydrogenase and delta 5-3 beta-hydroxy steroid dehydrogenase. Activity of 17 beta-hydroxy steroid dehydrogenase was not affected appreciably. Overall findings suggest that isoproturon, at high dose, impairs androgen biosynthetic process, affects spermatogenesis and induces maturational anomalies of sperm cells in rat.

Subacute toxicity of urea herbicide, isoproturon, in male rats.

Isoproturon, a substituted phenylurea herbicide, was evaluated for its cumulative toxic effect on growth, organ weight and histomorphology of different organs in adult male rats. The compound (200, 400 and 800 mg/kg/day for 6 days/week), suspended in refined groundnut oil, was administered to rats p.o. for 7 and 10 weeks. There were no definite signs and symptoms of toxicity in treated rats but the herbicide significantly decreased the weekly body weight of rats at 800 mg/kg dose. Isoproturon, in all the three doses, increased the weight of liver in a dose-dependent manner. At 800 mg/kg dose, isoproturon increased the weight of kidney and heart, and decreased the weight of epididymis. Histopathological alterations in the organs were dose-dependent. Salient microscopic changes induced by isoproturon were hepatocellular degenerative changes and focal necrosis in liver, glomerular and tubular degeneration in kidney and haemosiderosis in spleen. Testis showed degeneration and desquamation of cells of germinal layers. Tubular lumens of testis and epididymis exhibited reduced number of spermatids and spermatozoa, respectively, indicating retardation of spermatogenesis.

Neurotoxicity of isoproturon, a substituted phenylurea herbicide, in mice.

Effects of single oral administration of isoproturon (0.5, 1.0 and 2.0 g/kg) on CNS of male mice were studied. At higher doses, spontaneous motor activity (SMA) and forced locomotor activity (FLA) were reduced. Reduction of SMA and FLA was lesser than the reference drug-chlorpromazine hydrochloride (Ch. HCl; 15 mg/kg). Isoproturon, at all doses, potentiated both pentobarbital and barbital-induced sleeping time. At higher doses, potentiation of pentobarbital-induced hypnosis was comparable to Ch.HCl but isoproturon was more effective in inducing hypnosis with barbital. Isoproturon could not protect mice against amphetamine-induced aggregation toxicity. Isoproturon exhibited anticonvulsant activity against both supramaximal electroshock seizures and pentylenetetrazol-induced convulsions. It had no anticonvulsant activity against strychnine but only caused delay in onset of and protection from mortality. At higher doses, anticonvulsant action of isoproturon was comparable to diphenylhydantoin (50 mg/kg) and phenobarbital sodium (100 mg/kg). The study reveals that isoproturon has distinct inhibitory effect on central motor performance and sedative action on CNS. And also it has anticonvulsive and protective actions.

Fetotoxic and teratogenic potential of substituted phenylurea herbicide, isoproturon, in rats.

Effect of isoproturon (0.225, 0.45 and 0.90 g/kg/day) administered (po) from day 6 through 15 of gestation was studied on pregnant rats and their offsprings. There were no distinct clinical signs other than dose-related depression and drowsiness of pregnant rats. None of the animals died due to toxicity of isoproturon. At higher doses, decreased maternal body weight was observed during the advanced stage of pregnancy. The litter size, fetal weight and crown-rump and transumbilical lengths were decreased. There was increase in fetal resorption frequency and the number of fetuses with stunted growth. The compound had no effect on fetal sex ratio. No major visceral and skeletal malformations were observed. The study indicates fetotoxic potential of the compound.