Ornithine decarboxylase activity in the neonatal rat heart following prenatal exposure to ethylene glycol monomethyl ether

Toxicity review of ethylene glycol monomethyl ether and its acetate ester

Ethylene glycol monomethyl ether (EGME) and its acetate ester (EGMEA) are highly flammable, colorless, moderately volatile liquids with very good solubility properties. They are used in paints, lacquers, stains, inks and surface coatings, silk-screen printing, photographic and photo lithographic processes, for example, in the semiconductor industry, textile and leather finishing, production of food-contact plastics, and as an antiicing additive in hydraulic fluids and jet fuel. EGME and EGMEA are efficiently absorbed by inhalation as well as via dermal penetration. Dermal absorption may contribute substantially to the total uptake following skin contact with liquids or vapours containing EGME or EGMEA. EGMEA is rapidly converted to EGME in the body and the two substances are equally toxic in animals. Therefore, the two substances should be considered as equally hazardous to man. Effects on peripheral blood, testes, and sperm have been reported at occupational exposure levels ranging between 0.4 and 10 ppm EGME in air, and with additional, possibly substantial, dermal exposure. Severe malformations and disturbed hematopoiesis have been linked with exposure to EGME and EGMEA at unknown, probably high, levels. Embryonic deaths in monkeys and impaired spermatogenesis in rabbits have been reported after daily oral doses of 12 and 25 mg per kg body weight, respectively. In several studies, increased frequency of spontaneous abortions, disturbed menstrual cycle, and subfertility have been demonstrated in women working in the semiconductor industry. The contribution of EGME in relation to other exposure factors in the semiconductor industry is unclear.

Effects of 2-methoxyethanol on fetal development, postnatal behavior, and embryonic intracellular pH of rats

The industrial solvent 2-methoxyethanol (2ME) is a reproductive and developmental toxicant when administered by inhalation, gavage, and IP injection. The present research established that this solvent can produce teratogenicity in rats when administered in liquid diet. Groups of 10 Sprague-Dawley rats were given various percentages of 2ME in liquid diet on gestation days 7-18. Day 20 fetuses were examined for visceral or skeletal malformations. Concentrations above 0.025% 2ME (approximately 73 mg/kg/day) produced total embryo-mortality. Cardiovascular malformations were produced at lower levels. The teratogenic no-effect level was 0.006% 2ME (16 mg/kg). In a second experiment, groups of 12 Sprague-Dawley rats were given 0, 0.006 and 0.012% of 2ME as above. Litters were culled to 8 pups, and tested for auditory and tactile startle and conditioned lick suppression, and for performance in figure-8 activity and the Cincinnati water maze on postnatal days 48-65. The high dose of 2ME produced approximately 50% mortality in the offspring and increased the number of errors in the Cincinnati maze. No other behavioral effects were observed at either dose. An interaction study was conducted to determine if simultaneous exposure to 2ME and ethanol would reduce the teratogenicity of 2ME, but no reduction was observed. The hypothesis that 2ME acts by altering embryonic intracellular pH was tested by injecting 0.33 ml/kg of 2ME into rats on gestation day 13, and determining embryonic intracellular pH at 2, 4, 8, and 24 hours thereafter. There was an increase in pH at 4 hours, but not at later time points. Another group of rats was given 2ME along with amiloride, which blocks the sodium/hydrogen antiporter. The combined 2ME-amiloride exposure produced an incidence of cardiovascular malformations in fetuses twice that of 2ME alone. These studies confirmed the structural teratogenicity of 2ME even when given in liquid diet, as it was given for the first time in the present study. At nonteratogenic doses, developmental toxicity (e.g., postnatal deaths) persisted, but only limited evidence of behavioral teratogenicity was observed. The pH data are consistent with the concept that 2ME may alter embryonic intracellular pH at critical stages of organogenesis.

Prenatal ethylene glycol monomethyl ether (EGME) exposure produces electrocardiographic changes in the rat

The purpose of the present study was to determine if electrocardiographic (EKG) changes observed in fetuses exposed in utero to ethylene glycol monomethyl ether (EGME) persisted beyond the fetal/neonatal period. Groups of pregnant Sprague-Dawley rats were gavaged on gestation days 7-13 (sperm = day 0) with 0, 50, or 75 mg/kg EGME. Body weight prior to delivery was reduced and gestation was prolonged in EGME-treated dams. EGME treatment reduced the percentage of pregnant dams that delivered, litter size, and pup weight. There were no survivors beyond 3 days of age in the 75 mg/kg EGME group. The number of litters surviving through weaning and weight gain of male and female offspring through 8 weeks of age were reduced in the 50 mg/kg EGME group. In this same group, heart weight was unaffected, but heart/body weight ratios were increased when rats were 8 weeks old. EKGs were obtained from unanesthetized and unrestrained rats at 3 and 6 weeks of age. Prenatal EGME exposure increased the QRS interval in 3- and 6-week-old rats, and increased the T wave in 6-week-old rats. Thirty-six and 54% of 3- and 6-week old litters, respectively, had one or more individuals that were classified as having an intraventricular conduction delay (double R wave and QRS interval of 14 msec or longer). No microscopic heart abnormalities were associated with the observed intraventricular conduction delay.

Ethylene glycol monomethyl ether (EGME) inhibits rat embryo ornithine decarboxylase (ODC) activity

The effects of ethylene glycol monomethyl ether (EGME) on reproductive outcome in the rat, and on ornithine decarboxylase (ODC) activity in the rat embryo were evaluated. Dams (n = 8) were treated by gavage on gestation days 6-12 (sperm = day 0) with 0, 25, 50 or 75 mg/kg EGME in 10 ml/kg distilled water. EGME had a dose-dependent effect on reproductive outcome. Gestation length was prolonged, and the number of litters delivered and neonatal body weight were reduced. Whole embryo ODC was measured on gestation days 9, 11, 13 and 15. ODC attained maximum activity in controls on day 11, increasing by more than an order of magnitude above the activity found on day 9. On day 11, a statistically significant dose-dependent inhibition of ODC activity was observed with the maximum dose of EGME inhibiting ODC activity 60 percent. On days 13 and 15, ODC activity declined markedly from peak values, and the dose-dependent inhibition was no longer evident. The study demonstrates a correlation between the inhibition of embryonic ODC activity by EGME and the effect of EGME on reproductive outcome.