Sarin (Agent GB, isopropyl methylphosphonofluoridate) is an organophosphate cholinesterase inhibitor. Sarin (Type I or Type II) was administered by gavage to CD rats on d 6-15 of gestation at dose levels of 0, 100, 240, or 380 micrograms/kg/d and to New Zealand White (NZW) rabbits on d 6-19 of gestation at dose levels of 0, 5, 10, or 15 micrograms/kg/d. Females were weighed on gestational days (GD) 0, 6-16 for rats and 6-20 for rabbits, and immediately prior to termination (GD 20 for rats and GD 29 for rabbits). All animals were monitored daily for clinical signs of toxicity throughout dosing and until sacrifice. At necropsy, gravid uteri were weighed and examined for the number and status of implants (live, resorbed, or dead). Individual fetal body weight, malformations, and variations (external, visceral, and skeletal) were recorded. Rat and rabbit dams in the high-dose groups exhibited significant signs of maternal toxicity and increased maternal mortality. Examination of gravid uteri revealed no statistical differences among treatment groups in the incidence of resorptions or of dead or malformed fetuses, or in average body weight of live fetuses per litter. These results show no evidence or developmental toxicity in the CD rat or NZW rabbit following exposure to either Type I or Type II sarin during embryonic differentiation and major organogenesis, even at a dose that produced maternal toxicity.
Diisopropyl methylphosphonate (DIMP), produced during manufacture of the chemical agent GB (Sarin), is a groundwater contaminant at Rocky Mountain Arsenal, Colorado. DIMP was fed for 90 days to dark brown "Ranch Wild" mink housed under controlled indoor conditions. One-year-old mink, 10 of each sex, were fed 0, 50, 450, 2700, 5400, or 8000 ppm in standard ranch diet. Actual DIMP consumption was 0, 8, 73, 400, 827, and 1136 mg/kg body wt/day, respectively. Two additional groups of 10 served as "pair-fed" controls. Body weight and food intake were recorded weekly. Complete blood count and 15 chemical analytes were measured at Weeks 0, 3, 7, and 13. Necropsy and microscopic examination were performed on all mink. No clinical morbidity or deaths occurred. Both sexes fed 8000 ppm ate approximately 20% less and weighed approximately 20% less than the controls; 5400 ppm females had a 10% weight decrement. Plasma cholinesterase (ChE) decreased in the top three dose groups starting at Week 3. At 13 weeks, decrements were approximately 50% but returned to normal after 1 week without DIMP. Erythrocyte ChE was not reduced. Heinz bodies occurred in 10-15% of RBCs in 50% of 8000 ppm mink at 13 weeks, and 0.1-2.0% of RBCs in 25% at 2700 ppm. There were mild decreases in RBC count, hematocrit, and hemoglobin, and increases in reticulocyte count, at the 5400 and 8000 ppm doses. All recovered within 3 weeks after DIMP was withdrawn. The 8000 ppm group had marginal splenic hematopoiesis, histologically. No other treatment-related changes were noted. The 450 ppm dose was a clear no-effect level (approximately 73 mg DIMP/kg body wt/day). Compared to reports of similar studies of DIMP in rats and dogs, these mink displayed no unique species susceptibility.
Five mutagenicity tests were performed on Agent GA (Tabun, phosphoramidocyanidic acid, dimethyl-, ethyl ester) as part of a program to demilitarize chemical warfare agents. GA was mutagenic in Salmonella spp. assays with S-9 and it was a direct-acting mutagen to mouse lymphoma cells. GA did not promote unscheduled DNA synthesis in rat hepatocytes; it induced sister chromatid exchanges in mouse cells in vitro but in vivo. The conclusion that GA is a weakly acting mutagen is supported by the fact that it was mutagenic in only three of the five assays, and that increases in mutagenicity were often less than 2-fold the controls and occurred near toxic levels.
Title: Neurotoxicity of acute and repeated treatments of tabun, paraoxon, diisopropyl fluorophosphate and isofenphos to the hen Henderson JD, Higgins RJ, Dacre JC, Wilson BW Ref: Toxicology, 72:117, 1992 : PubMed
The neuropathic potential of acute and repeated exposures of the phosphoramidates tabun (GA) and isofenphos (IFP), of diisopropyl fluorophosphate (DFP) and paraoxon (PO) were examined in the hen with treatments for up to 90 days via intramuscular injections of the highest tolerated doses with atropine protection. Plasma acetylcholinesterase (AChE), non-specific butyrylcholinesterase (BChE) and creatine kinase (CK) activities were measured in order to monitor whether the compounds were present at biologically active concentrations. Locomotor behavior was observed and tissues from the peripheral and central nervous systems were examined for signs of organophosphate-induced delayed neuropathy (OPIDN). No behavioral or histological evidence of OPIDN was observed after treatments with GA, IFP, PO, saline or atropine sulfate. DFP-treated birds displayed locomotor and neuropathological signs of OPIDN with a no effect level (NOEL) between 25 and 50 micrograms/kg.
The neurotoxicities of single doses of a chemical warfare agent VX [phosphonothioic acid, methyl-S-(2-[bis(1-methylethyl)amino/ethyl) O-ethyl ester], a metabolite of the agricultural chemical parathion, paraoxon, PO (phosphonothioic acid, diethyl paranitrophenyl ester), and the known neuropathic agents DFP] phosphorofluoridic acid, bis(1-methylethyl) ester] and TOCP (phosphoric acid, tri-o-tolyl ester) were compared in the chicken. Single injections (subcutaneous, sc) of VX as high as 150 micrograms/kg (5 times the LD50, intramuscular, im) were tolerated by laying tens if atropine and 2-pralidoxime were used as antidotes before and immediately after injection. The 150 of VX for inhibition of chicken brain acetylcholinesterase was approximately 5 X 10(-10). Plasma acetylcholinesterase, but not butyrylcholinesterase, was depressed 2 h after injections of 2-20 micrograms VX/kg im without antidotes. Levels of plasma enzymes such as creatine kinase, indicative of tissue damage, were increased after exposure to both VX and PO. Injections of up to 150 micrograms/kg of VX with antidotes did not cause locomotor or histological signs of organophosphorus-induced delayed neuropathy, but single injections of 400 mg TOCP/kg did.
Hens were repeatedly exposed to paraoxon (PO, phosphonothioic acid, diethyl paranitrophenyl ester), the chemical warfare agent VX/phosphorofluoridic acid, methyl-S-(2-[bis(1-methylethyl)amino/ethyl)O-ethyl ester], or the neuropathic DFP [phosphorofluoridic acid, bis(1-methylethyl)ester] as evidence was sought for nerve or other tissue damage following long-term treatments at high dose levels. Thirty-day and 90-d trials were performed in which each bird was injected 3 or 5 times per week with atropine as protection, weighed, their eggs collected, and their blood enzymes (cholinesterases creatine kinase, and lactic dehydrogenase) and locomotion periodically examined. Muscle and brain enzymes were assayed at the end of the experiments. Doses of PO and VX were at or above LD50 levels. DFP doses were lowered with each run to estimate a no-observable-effect level for organophosphate-induced delayed-neuropathy (OPIDN). No abnormalities attributable to repeated exposures to either PO or VX were found, even though acute, short-term symptoms of toxicity appeared after each injection. No evidence for OPIDN was obtained with repeated exposures to PO and VX under conditions where OPIDN was caused by DFP. Histological signs of OPIDN appeared in the spinal cord without gross symptoms of ataxia following repeated treatments of 25 mg/kg of DFP. The results of one experiment suggested that exposure to protective injections of atropine delays the appearance of the locomotor symptoms of the DFP-induced neuropathy.
Title: Toxicology of some anticholinesterases used as chemical warfare agents - A review Dacre JC Ref: In: Cholinesterases, fundamental and applied aspects : proceedings of the Second International Meeting on Cholinesterases, (Brzin M, Barnard EA, Sket D, Eds) De Gruyter:415, 1984 : PubMed
