Pharmacological studies on the potentiation of phenytoin teratogenicity by acetaminophen

An in vivo murine model was developed to measure maternal phenytoin biotransformation along with the covalent binding of phenytoin to fetal tissues in the same fetuses which were assessed for fetal anomalies. Acetaminophen was administered to pregnant CD-1 mice 1 hour prior to phenytoin, both given i.p. at varying doses and gestational times between days 11 and 13. Dams were killed between days 12 and 19. Metabolites reflecting the enzymatic bioactivation of phenytoin were quantified in maternal plasma and urine with high-performance liquid chromatography (HPLC). Acetaminophen pretreatment caused a threefold increase in phenytoin-induced fetal cleft palates without increasing resorptions. The covalent binding of radiolabeled phenytoin to fetal and placental tissues measured on day 13 was increased twofold and threefold, respectively, by acetaminophen pretreatment. Phenytoin covalent binding measured on day 16 was significantly increased in the livers of fetuses with cleft palates, but not in the livers of dams with fetuses having cleft palates. Binding to fetal brain on day 16 was over fourfold higher than that in maternal brain. Acetaminophen pretreatment differentiated dams into poor and extensive metabolisers of phenytoin, with only the latter group carrying fetuses with cleft palates. The incidence of fetal cleft palates correlated positively with maternal urinary levels of phenytoin (r = +.81, P less than .01) and its dihydrodiol metabolite (r = +.61, 0.05 less than P less than .1), and negatively with levels of para-hydroxylated phenytoin (r = -.85, P less than .01). These findings related both to the mechanism of phenytoin teratogenicity and its potentiation by acetaminophen.     

Maternal administration of superoxide dismutase and catalase in phenytoin teratogenicity1

Embryonic bioactivation and formation of reactive oxygen species (ROS) are implicated in the mechanism of phenytoin teratogenicity. This in vivo study in pregnant CD-1 mice evaluated whether maternal administration of the antioxidative enzymes superoxide dismutase (SOD) and/or catalase conjugated with polyethylene glycol (PEG) could reduce phenytoin teratogenicity. Initial studies showed that pretreatment with PEG-SOD alone (0.5–20 KU/kg IP 4 or 8 h before phenytoin) actually increased the teratogenicity of phenytoin (65 mg/kg IP on gestational days [GD] 11 and 12, or 12 and 13) (p < .05), and appeared to increase embryonic protein oxidation. Combined pretreatment with PEG-SOD and PEG-catalase (10 KU/kg 8 or 12 h before phenytoin) was not embryo-protective, nor was PEG-catalase alone, although PEG-catalase alone reduced phenytoin-initiated protein oxidation in maternal liver (p < .05). However, time-response studies with PEG-catalase (10 KU/kg) on GDs 11, or 11 and 12, showed maximal 50-100% increases in embryonic activity sustained for 8-24 h after maternal injection (p < .05), and dose-response studies (10–50 KU/kg) at 8 h showed maximal respective 4-fold and 2-fold increases in maternal and embryonic activities with a 50 KU/kg dose (p < .05). In controls, embryonic catalase activity was about 4% of that in maternal liver, although with catalase treatment, enhanced embryonic activity was about 2% of enhanced maternal activity (p < .05). PEG-catalase pretreatment (10-50 KU/kg 8 h before phenytoin) also produced a dose-dependent inhibition of phenytoin teratogenicity, with maximal decreases in fetal cleft palates, resorptions and postpartum lethality at a 50 KU/kg dose (p < .05). This is the first evidence that maternal administration of PEG-catalase can substantially enhance embryonic activity, and that in vivo phenytoin teratogenicity can be modulated by antioxidative enzymes. Both the SOD-mediated enhancement of phenytoin teratogenicity, and the inhibition of phenytoin teratogenicity by catalase, indicate a critical role for ROS in the teratologic mechanism, and the teratologic importance of antioxidative balance.     

In vivo inhibition of l-buthionine-(S,R)-sulfoximine-induced cataracts by a novel antioxidant, N-acetylcysteine amide

The effects of N-acetylcysteine amide (NACA), a free radical scavenger, on cataract development were evaluated in Wistar rat pups. Cataract formation was induced in these animals with an intraperitoneal injection of a glutathione (GSH) synthesis inhibitor, l-buthionine-(S,R)-sulfoximine (BSO). To assess whether NACA has a significant impact on BSO-induced cataracts, the rats were divided into four groups: (1) control, (2) BSO only, (3) NACA only, and (4) NACA+BSO. The control group received only saline ip injections on postpartum day 3, the BSO-only group was given ip injections of BSO (4mmol/kg body wt), the NACA-only group received ip injections of only NACA (250mg/kg body wt), and the NACA+BSO group was given a dose of NACA 30min before administration of the BSO injection. The pups were sacrificed on postpartum day 15, after examination under a slit-lamp microscope. Their lenses were analyzed for selective oxidative stress parameters, including glutathione (reduced and oxidized), protein carbonyls, catalase, glutathione peroxidase, glutathione reductase, and malondialdehyde. The lenses of pups in both the control and the NACA-only groups were clear, whereas all pups within the BSO-only group developed well-defined cataracts. It was found that supplemental NACA injections during BSO treatment prevented cataract formation in most of the rat pups in the NACA+BSO group. Only 20% of these pups developed cataracts, and the rest retained clear lenses. Further, GSH levels were significantly decreased in the BSO-only treated group, but rats that received NACA injections during BSO treatment had these levels of GSH replenished. Our findings indicate that NACA inhibits cataract formation by limiting protein carbonylation, lipid peroxidation, and redox system components, as well as replenishing antioxidant enzymes.     

The in vivo biosynthesis of embryonic proteins after maternal administration of phenytoin in the mouse

Pregnant A/J mice received 60 mg phenytoin/kg body weight on Day 10 of gestation. Eighteen hours after phenytoin injection, animals were injected (ip) with 20 microCi/g of [35S]methionine. After 6 hr of incorporation animals were sacrificed and the embryos were removed. Protein synthesis in the embryo, as measured by [35S]methionine incorporation into trichloroacetic-precipitable protein, was analyzed by SDS-PAGE and quantitation of autoradiograms. The results of gel electrophoresis indicate that in embryonic primary palates and limb buds from phenytoin-treated mothers there is an increase in synthesis of 66-, 50-, 44-, and 13-kDa proteins and a decrease in synthesis of an 18-kDa protein compared with values for the control counterpart. No role has been assigned to the 66-, 44-, or 13-kDa proteins but the 50-kDa band comigrates with tubulin and the 18-kDa band comigrates with calmodulin. Palatal cells in vitro stained positively with specific antibody to both these proteins. An adverse effect of the anticonvulsant drug phenytoin, when administered to pregnant A/J mice is an increase in the incidence of cleft lip with or without cleft palate [CL(P)] in their offspring. These alterations in protein synthesis may be a direct or secondary result of maternal phenytoin treatment and may play a role in CL(P) formation in vivo.     

Palate teratogenicity and embryotoxicity of cyclosporin A in mice.

Mice of the A/J and B10.A/SgSnJ strains were treated with 50 mg of cyclosporin A (CsA) per kg of body weight on day 12 of gestation. There were significantly more fetal resorptions in both the A/J and B10.A strain when treated with CsA than in controls treated with olive oil. A low frequency (7.6%) of isolated cleft palates were induced in the A/J strain, which was significantly greater than that observed in A/J mice treated with olive oil alone. No cleft palates were induced in B10.A, which suggests that any increase in susceptibility that was observed could not be attributed to H-2 linked genes.     

Studies on the embryotoxicity and mutagenicity of mycotoxins

Embryotoxicity: Aflatoxin B₁(AFB₁), G₁ (AFG₁), and Patulin (PA) were investigated in NMRI mice for embryotoxic and teratogenic activity. These three mycotoxins were injected intraperitoneally or given orally on day 12 and 13 of pregnancy. AFB₁ (15, 45, and 90 mg/kg ip or 45 mg/kg po) produced a moderate retardation in the fetal development and a dose related increase of cleft palates, wavy ribs, and diaphragm changes. The effects after injection of AFG₁ (45 and 90 mg/kg ip) were reduction of fetal weights, increase of diaphragm changes, and malformations of kidneys. PA (1.25, 2.5, and 3.75 mg/kg ip or 3.75 mg/kg po) elevated the rate of cleft palates after 3.75mg/kg. In the dominant lethal assay neither PA (2.5 and 5 mg/kg ip) nor AFB₁) (15 and 45 mg/kg ip) increased the frequency of the dominant lethal mutations. Both mycotoxins showed no mutagenic activity in this test system. The capability of AFB₁, AFG₁, and PA to induce chromosome damages in vivo was tested in the Chinese Hamster by examination of bone marrow cells, each after two oral doses (AFB₁: 12.5 and 25 mg/kg; 25 and 50 mg/kg; PA: 10 and 20 mg/kg). The three mycotoxins induced chromosome aberrations in the following order of activity: PA > AFB₁ > AFG₁.     

Cardiomyocyte apoptosis induced by short-term diabetes requires mitochondrial GSH depletion

Oxidative stress due to excessive reactive oxygen species (ROS) and depleted antioxidants such as glutathione (GSH) can give rise to apoptotic cell death in acutely diabetic hearts and lead to heart disease. At present, the source of these cardiac ROS or the subcellular site of cardiac GSH loss [i.e., cytosolic (cGSH) or mitochondrial (mGSH) GSH] has not been completely elucidated. With the use of rotenone (an inhibitor of the electron transport chain) to decrease the excessive ROS in acute streptozotocin (STZ)-induced diabetic rat heart, the mitochondrial origin of ROS was established. Furthermore, mitochondrial damage, as evidenced by loss of membrane potential, increases in oxidative stress, and reduction in mGSH was associated with increased apoptosis via increases in caspase-9 and -3 activities in acutely diabetic hearts. To validate the role of mGSH in regulating cardiac apoptosis, L-buthionine-sulfoximine (BSO; 10 mmol/kg ip), which blocks GSH synthesis, or diethyl maleate (DEM; 4 mmol/kg ip), which inactivates preformed GSH, was administered in diabetic rats for 4 days after STZ administration. Although both BSO and DEM lowered cGSH, they were ineffective in reducing mGSH or augmenting cardiomyocyte apoptosis. To circumvent the lack of mGSH depletion, BSO and DEM were coadministered in diabetic rats. In this setting, mGSH was undetectable and cardiac apoptosis was further aggravated compared with the untreated diabetic group. In a separate group, GSH supplementation induced a robust amplification of mGSH in diabetic rat hearts and prevented apoptosis. Our data suggest for the first time that mGSH is crucial for modulating the cell suicide program in short-term diabetic rat hearts.     

Hepatic glutathione and nitric oxide are critical for hepatic insulin-sensitizing substance action

We tested the hypothesis that hepatic nitric oxide (NO) and glutathione (GSH) are involved in the synthesis of a putative hormone referred to as hepatic insulin-sensitizing substance HISS. Insulin action was assessed in Wistar rats using the rapid insulin sensitivity test (RIST). Blockade of hepatic NO synthesis with N(G)-nitro-l-arginine methyl ester (l-NAME, 1.0 mg/kg intraportal) decreased insulin sensitivity by 45.1 +/- 2.1% compared with control (from 287.3 +/- 18.1 to 155.3 +/- 10.1 mg glucose/kg, P < 0.05). Insulin sensitivity was restored to 321.7 +/- 44.7 mg glucose/kg after administration of an NO donor, intraportal SIN-1 (5 mg/kg), which promotes GSH nitrosation, but not after intraportal sodium nitroprusside (20 nmol x kg(-1) x min(-1)), which does not nitrosate GSH. We depleted hepatic GSH using the GSH synthesis inhibitor l-buthionine-[S,R]-sulfoximine (BSO, 2 mmol/kg body wt ip for 20 days), which reduced insulin sensitivity by 39.1%. Insulin sensitivity after l-NAME was not significantly different between BSO- and sham-treated animals. SIN-1 did not reverse the insulin resistance induced by l-NAME in the BSO-treated group. These results support our hypothesis that NO and GSH are essential for insulin action.     

Attempted modulation of disulfide antitumor activity in Balb/c mice through glutathione depletion

We investigated the effects of buthionine sulfoximine (BSO)-mediated glutathione (GSH) depletion on the antitumor activity in Balb/c mice produced by four disulfide derivatives of 6-TG and 6-MP. Initial studies indicated that 14 h after BSO (5 mmol/kg) injections, tumor GSH levels were maximally depleted, while normal tissue GSH levels had returned to near control levels. Tumor growth delays and growth rates were compared for groups of animals receiving disulfides I-IV with and without BSO administration 14 h previous. Treatments with BSO alone produced no delay or growth rate differences from the control. Compounds II or III administered in the presence and absence of BSO also produced no delay or growth rate differences from control. Compound I (10 mg/kg) alone showed a delay of 5.2 days and a growth rate significantly slower than that of control (p = 0.05). In combination with BSO the effects were not enhanced. Compound IV (50 mg/kg) also produced delays in 2 separate trials (3.1 and 4.8 days) and significantly slower growth rates on each occasion compared to the control (p = 0.05). The growth rates were not significantly lowered in the presence of BSO. Administration of two doses of IV, 4 days apart, produced a delay (4.9 days) similar to that seen with a single dose. It produced 2 cures and was also more toxic, causing 3 deaths. Two doses of IV in combination with BSO pretreatment had a greater delay (16.0 days) and a significantly longer growth rate (p = 0.05) than two doses of IV alone.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of the Ay gene on susceptibility to hydrocortisone fetotoxicity and teratogenicity in mice

Effects of the Ay gene, a coat color gene, on susceptibility to hydrocortisone fetotoxicity and teratogenicity were investigated by using the congenic strain of C57BL/6-Ay (Ay/a) which had been maintained by repeated back-crosses of the Ay gene to the C57BL/6 (a/a) background. Matings were conducted as follows (female x male): group I, a/a; group II, a/a x Ay/a; and group III, Ay/a x a/a. Pregnant females were subcutaneously given daily doses of 0, 12.5, 25, or 50 mg/kg of hydrocortisone on days 10-13 of pregnancy. On day 18 of pregnancy, fetuses were sexed, weighed, and examined for external abnormalities. In group I, the mean fetal weight was significantly decreased at a dose of 25 mg/kg or more. The incidences of cleft palate were 3.2 and 22.7% at 25 and 50 mg/kg, respectively. In group II, in which half of the fetuses were expected to carry the Ay gene, the mean fetal weight was decreased significantly at 12.5 mg/kg or more. The incidence of cleft palate in group II at 50 mg/kg was 44.2%, which was significantly higher than that in group I. In group III, in which maternal mice as well as half of their fetuses carried the Ay gene, a decrease in the mean fetal weight was greater than in group II. In addition, the mean percentage of fetal resorptions was significantly increased at 50 mg/kg. The incidence of cleft palate in group III was significantly increased at 25 mg/kg (10.5%) when compared with those in groups I and II. These results indicate that the Ay gene may be associated with susceptibility to hydrocortisone fetotoxicity and teratogenicity in mice.     

Effects of phorone and/or buthionine sulfoximine on teratogenicity of 5-fluorouracil in mice

Embryotoxicity and teratogenicity of 5-fluorouracil (5-FU) and modulation of its effect by the depletors of glutathione (GSH) were evaluated in mice. Pregnant ICR mice were intraperitoneally (i.p.) injected with 25 mg/kg of 5-FU on day 11 of gestation (vaginal plug = day 0). Mice were pretreated i.p. with 250 mg/kg of phorone, a GSH depleting agent and/or 200 mg/kg of buthionine sulfoximine (BSO, an inhibitor of GSH biosynthesis) 4 hours before dosing with 5-FU. Dams were killed on day 17 of gestation. Fetuses were examined for external malformations, especially limb malformations. Pretreatment with phorone or BSO decreased fetal weight and increased the frequency and severity of oligodactyly induced by 5-FU, as well as the reduction of maternal GSH levels. Combined use of 125 mg/kg phorone and 100 mg/kg BSO i.p. augmented growth retardation induced with 5-FU. Cotreatment with exogenous GSH, at a dose of 300 mg/kg injected intravenously, could not suppress the augmentative effects of phorone and/or BSO on 5-FU teratogenicity under these experimental conditions. These results indicate that the level of endogenous GSH is one of the factors which significantly affects teratogenicity of 5-FU.     

H-2 histocompatibility region influences the inhibition of arachidonic acid cascade by dexamethasone and phenytoin in mouse embryonic palates

We have reported that susceptibility to glucocorticoid- and phenytoin-induced cleft palate and glucocorticoid receptor levels in mice are influenced by the H-2 histocompatibility complex on chromosome 17. Phenytoin competes with glucocorticoids for the glucocorticoid receptor and inhibits production of prostaglandins and thromboxanes. In this paper, we have investigated whether glucocorticoids and phenytoin inhibit arachidonic acid release and prostaglandin biosynthesis directly in the embryonic palates and whether the H-2 gene complex influences the degree of inhibition. Using congenic strains varying only in the H-2 region, we demonstrate here that both glucocorticoids and phenytoin inhibit the release of 3H-arachidonic acid and prostaglandin biosynthesis from embryonic palatal tissue, prelabeled with 3H-arachidonic acid. The degree of inhibition of arachidonic acid release and of prostaglandin biosynthesis is greater in the strain with H-2a (A/Wy) than in its corresponding congenic partner H-2b (A.BY). Thus, these results provide further evidence for a similar genetic and biochemical pathway for the teratogenic action of both phenytoin and glucocorticoids.     

Comparison of cleft palate induction by Nicotiana glauca in goats and sheep

The induction of cleft palate by Nicotiana glauca (wild tree tobacco) during the first trimester of pregnancy was compared between Spanish-type goats and crossbred western-type sheep. Cleft palate was induced in 100% of the embryonic/fetal goats when their pregnant mothers were gavaged with N. glauca plant material or with anabasine-rich extracts from the latter, during gestation days 32-41. Seventy-five percent of newborn goats had cleft palate after maternal dosing with N. glauca during gestation days 35-41, while no cleft palates were induced when dosing periods included days 36-40, 37-39, or day 38 only. The induced cleft palates were bilateral, involving the entire secondary palates with complete detachment of the vomer. Eleven percent of the newborn goats from does gavaged during gestation days 32-41 had extracranial abnormalities, most often contractures of the metacarpal joints. Most of these contractures resolved spontaneously by 4-6 weeks postpartum. One newborn kid also had an asymmetric skull due to apparent fetal positioning. No cleft palates were induced in lambs whose mothers were gavaged with N. glauca plant or anabasine-rich extracts during gestation days 34-41, 35-40, 35-41, 36-41, 35-51, or 37-50. Only one of five lambs born to three ewes gavaged with N. glauca plant material during gestation days 34-55 had a cleft palate, but all five of these lambs had moderate to severe contractures in the metacarpal joints. The slight to moderate contracture defects resolved spontaneously by 4-6 weeks postpartum, but the severe contractures resolved only partially. Embryonic/fetal death and resorption (determined by ultrasound) occurred in 25% of pregnant goats fed N. glauca compared to only 4% of pregnant sheep. Nicotiana glauca plant material contained the teratogenic alkaloid anabasine at 0.175% to 0.23%, dry weight, demonstrating that Spanish-type goats are susceptible to cleft palate induction by the natural toxin anabasine, while crossbred western-type sheep are resistant. However, clinical signs of toxicity were equally severe in goats and sheep, even though maternal alkaloid tolerance was generally lower in sheep. We postulate that an alkaloid-induced reduction in fetal movement during the period of normal palate closure is the cause of the cleft palate and multiple flexion contractures. Teratology 61:203-210, 2000. Published 2000 Wiley-Liss, Inc.     

Teratological interaction between the bis-triazole antifungal agent fluconazole and the anticonvulsant drug phenytoin

Previous studies implicated the cytochrome P450 (CYP) system as critical in the teratogenic bioactivation of phenytoin (PHT). Fluconazole (FCZ) is an antifungal bis-triazole with potent inhibitory effect on the principal CYP-dependent metabolic pathway of PHT. In this study an in vivo experimental model was used to evaluate the potential ability of FCZ (2, 10, or 50 mg/kg intraperitoneally) to modulate PHT (65 mg/kg intraperitoneally) teratogenesis on day 12 (plug day = day 1) Swiss mice. PHT alone elicited embryocidal and malformative effects, with cleft palate as the major malformation. Pretreatment with the nonembryotoxic dosage of 10 mg FCZ/kg potentiated PHT-induced teratogenesis, as indicated by a twofold (from 6.2% to 13.3%) increment of cleft palate incidence (P < 0.05). Combined treatment with 50 mg FCZ/kg plus PHT resulted in a statistically significant (P < 0.05) increment of the resorption incidence recorded after PHT-alone exposure, but possibly as a consequence of the increased embryolethality, in the loss of the potentiative effect on PHT teratogenesis. Although the mechanistic nature of teratological interaction between FCZ and PHT remains to be established, these results may not support CYP system-mediated metabolic conversion as the mechanistic component of PHT teratogenesis.     

Teratogenic effects of the plant hormone indole-3-acetic acid in mice and rats.

These studies evaluated the teratogenic potential of indole-3-acetic acid (IAA), a naturally occurring plant hormone, in CF-1 mice and Sprague-Dawley rats. Mice were given 5, 50, 200, or 500 mg IAA/kg/day by gavage on days 7 through 15 of gestation. Rats were given 50, 200, or 500 mg IAA/kg/day by gavage on days 7 through 15 of gestation. IAA was teratogenic in mice and rats at 500 mg/kg/day; cleft palate was induced in both species at this dose level. In mice, other malformations including exencephaly, ablepharia, dilated cerebral ventricles, and crooked tail were also observed. Mice given 500 mg/kg of IAA gained less than control mice during gestation; no evidence of maternal toxicity was observed in rats. IAA did not cause fetal resorptions in either species and was not teratogenic at dose levels below 500 mg/kg.     

Aging reduces responsiveness to BSO- and heat stress-induced perturbations of glutathione and antioxidant enzymes

Aging alters cellular responses to both heat and oxidative stress. Thiol-mediated metabolism of reactive oxygen species (ROS) is believed to be important in aging. To begin to determine the role of thiols in aging and heat stress, we depleted liver glutathione (GSH) by administering l-buthionine sulfoximine (BSO) in young (6 mo) and old (24 mo) Fisher 344 rats before heat stress. Animals were given BSO (4 mmol/kg ip) or saline (1 ml ip) 2 h before heat stress and subsequently heated to a core temperature of 41 degrees C over a 90-min period. Liver tissue was collected before and 0, 30, and 60 min after heat stress. BSO inhibited glutamate cysteine ligase (GCL, the rate-limiting enzyme in GSH synthesis) catalytic activity and resulted in a decline in liver GSH and GSSG that was more pronounced in young compared with old animals. Catalase activity did not change between groups until 60 min after heat stress in young BSO-treated rats. Young animals experienced a substantial and persistent reduction in Cu,Zn-SOD activity with BSO treatment. Mn-SOD activity increased with BSO but declined after heat stress. The differences in thiol depletion observed between young and old animals with BSO treatment may be indicative of age-related differences in GSH compartmentalization that could have an impact on maintenance of redox homeostasis and antioxidant balance immediately after a physiologically relevant stress. The significant changes in antioxidant enzyme activity after GSH depletion suggest that thiol status can influence the regulation of other antioxidant enzymes.     

Short-term oral exposure to aluminium decreases glutathione intestinal levels and changes enzyme activities involved in its metabolism

To study the effects of aluminium (Al) on glutathione (GSH) metabolism in the small intestine, adult male Wistar rats were orally treated with AlCl3.6H2O at doses of 30, 60, 120 and 200 mg/kg body weight (b.w.) per day, during seven days. Controls received deionized water. At doses above 120 mg/kg b.w., Al produced both a significant reduction of GSH content and an increase of oxidized/reduced glutathione ratio (P < 0.05). The index of oxidative stress of the intestine mucosa in terms of lipid peroxidation evaluated by thiobarbituric acid reactive substances was significantly increased (52%) at higher Al dose used. The duodenal expression of the multidrug resistance-associated protein 2 in brush border membranes, determined by Western blot technique, was increased 2.7-fold in rats treated with 200mg AlCl3/kg b.w (P < 0.01). Intestine activities of both GSH-synthase (from 60 mg/kg b.w.) and GSSG-reductase (from 120 mg/kg b.w.) were significantly reduced (26% and 31%, respectively) while glutathione-S-transferase showed to be slightly modified in the Al-treated groups. Conversely, gamma-glutamyltranspeptidase activity was significantly increased (P < 0.05) due to the Al treatment. Al reduced in vitro mucosa-to-lumen GSH efflux (P < 0.05). A positive linear correlation between the intestine GSH depletion and reduction of in situ 45Ca intestinal absorption, both produced by Al, was found (r = 0.923, P = 0.038). Taking as a whole, these results show that Al would alter GSH metabolism in small intestine by decreasing its turnover, leading to an unbalance of redox state in the epithelial cells, thus contributing to deteriorate GSH-dependent absorptive functions.     

Maternal and developmental toxicity of low doses of cytosine arabinoside in mice

1-beta-D-Arabinofuranosylcytosine (Ara-C), an effective drug for the treatment of leukemia and breast cancer, was evaluated for developmental toxicity in pregnant Swiss mice. Ara-C was administered by intraperitoneal injection on gestational days 6-15 at doses of 0, 0.5, 2, and 8 mg/kg/day. Maternal observations included clinical signs, body weight change, food consumption, and gross evaluation of organs and uterine contents at necropsy (day 18). Live fetuses were examined for external, visceral, and skeletal alterations. Maternal toxicity was observed at 2 and 8 mg/kg/day, as evidenced by a significant decrease in body weight gain and food consumption during the treatment period. Significantly increased early and late resorptions and reduced number of live fetuses per liter as well as decreased fetal body weight were observed at 8 mg/kg/day. At 2 mg/kg/day, the incidence of cleft palate, renoureteral agenesis or hypoplasia, and poly- or oligodactyly was significantly increased, whereas fetal weight was reduced at 0.5 mg/kg/day. Thus, the developmental no-observed-adverse-effect-level (NOAEL) of Ara-C in the pregnant mouse is lower than 0.5 mg/kg/day, while the NOAEL for maternal toxicity is 0.5 mg/kg/day. We believe that exposure to this agent ought to be avoided during organogenesis.     

Maternal phenytoin administration affects DNA and protein synthesis in embryonic primary palates

Recent studies have shown that phenytoin (Dilantin) administration to pregnant A/J mice on day 10 causes reduced growth in embryonic primary palates. The current investigation concentrates on biochemical and autoradiographic changes toward the end of primary palate formation (gestational day 11), which coincides with the developmental period used for the previously conducted morphological studies. On gestational day 10, one group of pregnant A/J mice was injected intraperitoneally (IP) with 60 mg/kg phenytoin and the other group with vehicle. Twenty-three hours after phenytoin administration, all animals were injected (IP) with either [3H]-thymidine or [3H]-leucine. After one hour of incorporation, animals were sacrificed, embryos removed and placed in ice-cold Eagle's minimum essential medium containing 0.02% NaN3 for biochemical assay or fixed immediately in Bouin's solution for autoradiography. For biochemical analyses, palates and limb buds were removed, homogenized, TCA precipitated, lyophilized, and acid hydrolyzed. Examination of the data revealed that DNA synthesis in control palates was 3.8-fold greater than in primary palates from embryos of phenytoin-treated mothers. Results were similar for limb buds from control embryos and from embryos of phenytoin-treated mothers. Experiments utilizing [3H]-leucine indicated that protein synthesis was 2.6-fold greater in primary palates from phenytoin-treated mothers than in control primary palates. Similar results were obtained for protein synthesis in limb-bud tissue from controls and embryos of phenytoin-treated mothers. Autoradiographic data supported the biochemical findings. DNA synthesis in primary palates from embryos of phenytoin-treated mothers decreased 3-fold; protein synthesis increased 2.2-fold compared with control primary palates.(ABSTRACT TRUNCATED AT 250 WORDS)