Reaction mass of 9-icosyl-9-phosphabicyclo[3.3.1]nonane and 9-icosyl-9-phosphabicyclo[4.2.1]nonane

Neurotoxicity

Description of key information

3 neurotoxicity studies are available to determine whether single or repeated dermal application of molten RM-17 either on its own (report TLGR.0173.78), in toluene (report TLGR.79.028) or in n-butanol (report TLGR.79.030)  resulted in in clinical, functional or electrophysiological changes consistent with peripheral neuropathy.1 neurotoxicity report (TLGR.0172.78) is available to determine whether acute or subacute oral administration of molten RM-17 affects the performance of rats in a test designed to assess neuromuscular dysfunction.         

Additional information

Dewar AJ & Moffett BJ (1979): A functional study of the neurotoxicity of dermally applied RM-17 (9 -eicosyl-9 -phophabicyclo [4.2.1] [3.3.1.] Nonane) to rats. Shell Toxicology Laboratory, Report. TLGR.0173.78

Twelve Wistar rats ( 6 male and 6 female) received 16 dermal doses of 4 ml/kg molten RM-17 (45°C) over a period of 33 days. Eight rats (4 male and 4 female) dosed with molten paraffin wax (45°C) at the same time served as controls. The RM-17 dosed animals showed no obvious clinical signs of a peripheral neuropathy neither during the dosing period nor for 35 days after dosing had stopped. During the 67 day experimental period their performance on the narrowing bridge test was indistinguishable from that of the controls thus suggesting that these animals were not suffering from any sub-clinical neuromuscular dysfunction. The sciatic nerve maximal motor conduction velocity (MCV) of each animal was measured one during the dosing period and once after dosing had stopped. At no time were the MCVs of the RM-17 dosed animals less than those of the controls (mean values 52.0 ± 2.8 and 52.9 ± 2.8 m/sec respectively).

 

It is concluded that 16 dermal doses of 4 ml/kg molten RM-17 produces no clinical, functional or electrophysiological signs of peripheral neuropathy. It would appear therefore that dermally applied molten RM-17 does not result in overt peripheral neuropathy as measured by parameters studied in this experiment. This contasts with results obtained following oral exposure to molten RM-17.  

 

Dewar AJ, Moffett BJ, & Baldwin MK (1979): The neurotoxicity of dermally applied RM-17 solutions to rats I: The effect of RM-17 as a 25% solution in toluene. Shell Toxicology Laboratory, Report. TLGR.79.028

Groups of rats were given either a single dermal dose of 16 ml/kg or 5 doses of 8 ml/kg of a 25% solution of RM-17 in toluene. Control groups received either 16 ml/kg or 5 x 8 ml/kg toluene. A further group (positive control) received two oral doses of 4 ml/kg molten RM-17. Body weights, clinical signs of intoxication and ther performance of half of the animals on a narrowing bridge apparatus were recorded over a 32 day period. During this period the maximal motor conduction velocity (MCV) in the sciatic nerve was measured on at least one occasion. The remaining animals were killed 3-4 weeks after dosing and β-glucuronidase and β-galactosidase were measured in digital and proximal sections of the sciatic/posterior tibial nerve, the trigeminal ganglia and the optic nerve.

 

1. A single massive (16 ml/kg) dermal exposure to a 25% solution of RM-17 in toluene gave rise to no clinical, functional, biochemical or electro-physiological changes suggestive of peripheral neuropathy.

 

2. Five dermal doses of 8 ml/kg 25% RM-17 in toluene (roughly equivalent, in terms of RM-17, to the neurotoxic oral dose given to the ‘Positive’ controls) resulted in severe skin irritation and a pronounced (>20%) loss in bodyweight. However after dosing ceased, the rate of weight gain was similar to that of the controls. The animals had a slight ‘tip-toe’ gait but this was transient and no functional deficit was observable. There was no biochemical evidence of neuropathy but 2 of the 8 animals investigated electrophysiologically had a consistently reduced MCV in the sciatic nerve.

 

3. Two oral doses of 4 ml/kg molten RM-17 resulted in a dramatic weight loss (>35%), clinical signs suggestive of severe peripheral neuropathy (eg hind limb incoordination and paralysis) and a very pronounced functional deficit on the narrowing bridge test. Thirteen of the 16 animals died within 14 days of dosing. Biochemical changes consistent with extensive Wallerian degeneration were found in the sciatic/posterior tibial nerve and trigeminal ganglion and evidence of degeneration was also apparent in the optic nerve. All the animals which survived to be investigated electrophysiologically had sciatic nerve values approximately 20% below the controls. This observation is also consistent with extensive Wallerian degeneration.

 

4. It is concluded that the dermal application of RM-17 as a 25% solution in toluene, even in doses approximating to a highly neurotoxic oral dose, has only a marginally neurotoxic effect on mature Wistar rats.

 

5. Some penetration of RM-17 applied dermally as a 25% solution in toluene does occur. Residues were detected in fat four months after application and the half life in fat was greater than 18 days.

Dewar AJ & Moffett BJ (1979): The neurotoxicity of dermally applied RM-17 solutions to rats II. The effect of RM-17 as a 5% solution in n-butanol, Shell Toxicology Laboratory, Report. TLGR.79.030

Groups of rats were given either a single dermal dose of 16 ml/kg or 5 doses of 8 ml/kg of a 5% solution of RM-17 in butanol. Control groups received either 16 ml/kg or 5 x 8 ml/kg butanol. A further group (positive control) received two oral doses of 4 ml/kg molten RM-17. Body weights, clinical signs of intoxication and the performance of half of the animals on a narrowing bridge apparatus were recorded over a 32 day period. During this period the maximal motor conduction velocity (MCV) in the sciatic nerve was measured on at least one occasion. The remaining animals were killed 3-4 weeks after dosing and β-glucuronidase and β-galactosidase were measured in distal and proximal sections of the sciatic/posterior tibial nerve, the trigeminal ganglia and the optic nerve.

 

1. A single massive (16 ml/kg) dermal exposure of rats to a 5% solution of RM-17 in n-butanol resulted in a transient 5-10% loss in body weight but no clinical signs suggestive of neuropathy. The rats showed no functional deficit or biochemical evidence of nerve damage. The sciatic nerve MCVs, were all in the control range.

 

 

2.  Ten of the 16 animals dosed repeatedly with 8 ml/kg 5% RM-17 in n-butanol died during the dosing period. The manner of death suggested n-butanol intoxication rather than RM-17 intoxication. None of these animals, or the survivors, showed any consistent clinical signs suggestive of neuropathy. The surviving animals gained weight after dosing ceased and at no time showed functional deficit on the narrowing bridge test. Biochemical changes consistent with sparse axonal damage were found in the proximal section of the sciatic nerve and trigeminal ganglia but these changes were very small compared with those found in the positive controls.

 

3. The rats given 2 x 4 ml/kg RM-17 p.o showed clinical signs of intoxication consistent with severe neuropathy. They showed a pronounced functional deficit and had biochemical changes in the sciatic/posterior tibial nerve, trigeminal ganglion and optic nerve consistent with extensive Wallerian degeneration. The sciatic nerve MCVs were lowered by approximately 20% - an observation also consistent with extensive Wallerian degeneration. Eleven of the sixteen animals died.

Dewar AJ & Moffett BJ (1979): A functional study of the neurotoxicity of orally administered RM-17 (9 -Eicosyl-9 -phosphabicyclo (4.2.1.) (3.3.1.) nonane) to rats, Shell Toxicology Labortory, Report TLGR.0172.78

Groups of rats given doses of molten RM-17 ranging from a single dose of 2 ml/kg to four doses of 4 ml/kg were tested regularly on a narrowing bridge apparatus and their performance compared with that of undosed controls. Records of body weights and signs of intoxication were kept and clinical electrophysiological measurements were made on animals showing clinical signs suggestive of peripheral neuropathy.

 

1. A single oral dose of 2 ml/kg moltrn RM-17 produced no clinical signs of intoxication, no functional deficit and no appreciable loss in body weight.

 

2. A single oral dose of 4 ml/kg molten RM-17 produced no obvious clinical signs of intoxication, a marginal and reversible functional deficit in some animals and a small reduction in the rate of weight gain.

 

3. Two consecutive daily doses of 4 ml/kg molten RM-17 resulted in sever clinical signs of intoxication in the majority of the animals thus dosed. All animals showed a dramatic loss of weight (>20% within one week of dosing) and half of them died within two weeks, after suffering from hind limb incoordination, ataxia, and a gross functional deficit. Two of the survivors developed a flailing hypotonic gait, and severe ataxia. They had a gross functional deficit on the narrowing bridge test and a reduced maximal motor conduction velocity (MCV) in the sciatic nerve. These two animals were observed over a 2-4 month period and neither animal showed any evidence (clinical, functional or electrophysiological) of recovery. Of the two survivors, neither had shown clinical signs of intoxication suggestive of a peripheral neuropathy. Both showed only a marginal functional deficit although one did appear to have a reduced sciatic nerve MCV.

 

4. Four consecutive daily doses of 4 ml/mg molten RM-17 resulted in the deaths of all animals within 2 weeks. All animals showed dramatic weight loss (30-40%) and gross functional deficit with severe signs of intoxication including hind limb incoordination and gross ataxia.

 

5. It is concluded that repeated oral doses of 4 ml/kg molten RM-17 to rats produces clinical, functional and electrophysiological changes consistent with severe peripheral nerve damage. Evidence from the surviving animals suggests that this peripheral neuropathy is not reversible within a period of 2-4* months. The evidence from this study (in conjunction with the evidence from an earlier biochemical study) suggests that s ingle dose of 4 ml/kg produces sparse axonal degeneration in peripheral nerve but the degree of nerve damage is insufficient to produce any obvious clinical signs or a pronounced functional deficit.

*Further evidence suggests that no recovery occurs within a period of 8 months (please see details on results for further information).