A 2-year inhalation study of phosphine in rats

Phosphine is a highly toxic gas used as a fumigant, a dopant in semiconductor manufacturing, and in the production of organophosphines. In a chronic toxicity and oncogenicity study of phosphine, 60 male and female F344 rats per group were exposed via whole-body inhalation for 6 h/day, 5 days/wk for up to 104 wk to mean concentrations of 0, 0.3, 1, or 3 ppm phosphine. Three parts per million was considered the maximum exposure level because of lethality seen at higher exposure levels in previous repeat dose studies. Ten rats per sex per group were sacrificed after 52 wk of exposure. Survivors were sacrificed after 104 wk of exposure. There were no phosphine-related effects seen on clinical observations, body weight, food consumption, hematology, clinical chemistry, urinalysis, or ophthalmology. There were no phosphine-related macroscopic findings or effect on absolute or relative organ weights. No histomorphologic alterations attributable to phosphine exposure were seen. In conclusion, under the conditions of this study, there were no treatment-related changes suggestive of a toxic or carcinogenic effect seen in rats following 52 wk or 2 yr of whole-body inhalation exposure to 0.3, 1, or 3 ppm phosphine.

Toxicity of a low level of indium phosphide (InP) in rats after intratracheal instillation

To clarify the instillation toxicity of low level of indium phosphide (InP), 0, 1.2, 6.0 and 62.0 micrograms/kg body weight of InP particles were instilled intratracheally in male Fischer 344 rats, and the effects of InP were examined on the following day (day 1) and on the 8th day (day 8) after instillation. Indium was measured but not detected in the serum, liver, kidney, spleen, thymus and brain. Dose-related mild elevation of superoxide dismutase (SOD) activity and lactate dehydrogenase (LDH) activity in bronchoalveolar lavage fluid (BALF) were found on day 1 without increases of inflammatory cells and total protein (TP) in BALF, which suggested the response of neutrophils and alveolar macrophages to instilled InP, and/or the manifestation of a very early stage of inflammation. Only in the 62.0 micrograms/kg-instilled group on day 8, were neutrophils, lymphocytes, TP, LDH, total phospholipid and total cholesterol in BALF increased, and desquamation of alveolar epithelial cells and amorphous exudate in alveolar lumen observed by histopathological examination. These results suggested that InP caused pulmonary inflammation and epithelial cell damage up to 8 days following instillation dose of 62.0 micrograms/kg, but that its effect was considered irrelevant at instillation doses of 6.0 micrograms/kg or below in rat.

Tissue distribution and elimination of indium in male Fischer 344 rats following oral and intratracheal administration of indium phosphide

The use of indium phosphide (InP) in the semiconductor industry has raised concerns about potential occupational exposure. The tissue distribution and elimination of indium were investigated in adult male Fischer 344 rats following either a single or 14 consecutive daily oral doses, or following an intratracheal instillation of InP (10 mg/kg). The concentrations of indium ions in blood, urine, feces, and tissues were quantified either using direct acid digestion followed by electrothermal atomic absorption spectrophotometry (ET-AAS) or using an extraction method with methyltricapryl ammonium ions to remove indium from the matrix followed by ET-AAS. Indium was poorly absorbed from the gastrointestinal tract in both single and multiple oral dose studies. Upon its absorption, indium was relatively evenly distributed among the major organs such as liver, kidney, lung, spleen, and testes. By 96 h after oral dose treatment, less than 0.11% of the dose of indium was recovered from tissues in the single- or multiple-dose experiment. At 96 h, retention of indium in the body was about 0.36% of the dose (except for lung) following intratracheal instillation of InP. Following oral dose administration, the majority of indium was recovered from the gastrointestinal tract and its contents. The high recovery of indium (73% of the dose) in the feces after intratracheal instillation presumably reflects mucociliary clearance and/or biliary excretion of indium. Urinary indium accounted only for 0.08-0.23% of the dose during a 240-h collection period in both single- and multiple-dose studies. It seems that fecal excretion serves as the major route for indium elimination, and this results from poor absorption. Because of the poor absorption of indium following multiple oral doses or intratracheal instillation of InP, it seems unlikely that indium will accumulate in the body following InP exposure.

Determination of genotoxic and other effects in mice following short term repeated-dose and subchronic inhalation exposure to phosphine

Phosphine is an important fumigant in the grain industry and has been reported to be genotoxic in occupationally exposed fumigators. This study reports on the effects of phosphine inhalation exposure at up to, and exceeding, occupational relevant levels in a subchronic (0.3, 1.0 and 4.5 ppm, 13 weeks) and a short term repeated-dose (5.5 ppm, 2 weeks) study in both sexes of Balb-c mice. The following end-points were examined: micronucleus induction in bone marrow, peripheral blood, spleen lymphocytes and skin keratinocytes, mutations at the hypoxanthine-guanine phosphoribosyl transferase locus in lymphocytes, and weight gain and relative organ weights (kidneys, lungs, liver, heart, brain and spleen). After subchronic exposure, there was a highly significant negative linear correlation between proportional weight gain and exposure in both sexes (multiple linear regression, r = -0.56, P < 0.0001), with female mice showing a greater effect. Females also showed an increase in relative organ weights at the highest test dose, in contrast to males where there was a slight decrease. A statistically significant increase in micronucleus frequency was seen in the bone marrow and spleen lymphocytes of both sexes, but only at the highest concentration. The short term repeated-dose study revealed a slight decrease in weight gain in both sexes, with a greater effect in females. It is concluded that phosphine is weakly genotoxic in both sexes of mice, and has an effect on weight gain. However, the weak genotoxic effect may not be biologically significant as it was seen only in the subchronic study and only at the highest test concentration of 4.5 +/- 0.8 ppm (approaching the LD50). Although such exposure conditions are unlikely to be encountered in an occupational environment, caution should continue to be exercised in the use of phosphine until more data become available.

Cytogenetic effects of phosphine inhalation by rodents. I: Acute 6-hour exposure of mice

Phosphine (PH3) is a highly toxic grain fumigant that can be produced from the reaction of metal phosphides with water. To determine the in vivo cytogenetic effects of inhalation of PH3, male CD-1 mice were exposed to either 0, 5, 10, or 15 ppm target concentrations of PH3 for 6 hr. Twenty hours after the termination of exposure, the spleens of the mice were removed, macerated, and the splenocytes cultured for analyses of sister chromatid exchanges, chromosome aberrations, and micronuclei in cytochalasin B-induced binucleated cells. In addition, bone marrow smears were made for the analysis of micronuclei in polychromatic erythrocytes. No increase in any of the cytogenetic endpoints was found at any of the concentrations examined. The only statistically significant response was a concentration-related slowing of the cell cycle in the splenocytes.

Cytogenetic and germ cell effects of phosphine inhalation by rodents: II. Subacute exposures to rats and mice

Phosphine (PH3) is a highly toxic grain fumigant to which there is significant human workplace exposure. To determine the in vivo cytogenetic effects of inhalation of PH3, male F344/N rats and B6C3F1 mice were exposed to target concentrations of 0, 1.25, 2.5, or 5 ppm PH3 for 6 hr/day for 9 days over an 11-day period. Approximately 20 hr after the termination of exposures, blood was removed from the mice and rats by cardiac puncture and the lymphocytes cultured for analyses of sister chromatid exchanges and chromosome aberrations in rats and mice, and micronuclei (MN) in cytochalasin B-induced binucleated lymphocytes from mice. In addition, bone marrow (rats) and peripheral blood (mice) smears were made for the analysis of MN in polychromatic and normochromatic erythrocytes. No significant increase in any of the cytogenetic endpoints was found at any of the concentrations examined. These results indicate that concentrations of PH3 up to 5 ppm are not genotoxic to rodents when administered by inhalation for 9 days during an 11-day period as measured by several cytogenetic assays. To evaluate the effects of PH3 on male germ cells, a dominant lethal test was conducted in male mice exposed to 5 ppm PH3 for 10 days over a 12-day period and mated to groups of untreated females (2 females/male) on each of 6 consecutive 4-day mating intervals. None of the 6 groups of females exhibited a significant increase in percent resorptions. These results indicate that exposure to 5 ppm PH3 by inhalation does not induce dominant lethality in male mouse germ cells at steps in spermatogenesis ranging from late differentiating spermatogonia/early primary spermatocytes through mature sperm.

Toxicity of exposed aluminium phosphide

Poisoning by the partially or fully exposed compound of aluminium phosphide (ALP) is becoming common, Fifty patients with history of ingestion of ALP either in the form of broken tablets or granular powder were included in this study for analysis of systemic effects and outcome. Forty patients (Gr. I) consumed broken or granular form of tablets. Ten patients (Gr. II) consumed only powder form of tablets from an old container. 30 patients in group-I developed mild hypotension (BP 80-90 mm Hg). 4 patients (10%) developed ECG changes and mild metabolic acidosis. One patient died constituting 2.5% mortality rate. The patients of group-II neither developed any systemic effects nor showed any mortality. The aim of the study is to differentiate these cases from patients who consume active, fresh compound where mortality rate will be much higher.

[Combined chronic toxicity/carcinogenicity test of tris(2-chloroethyl)phosphate (TCEP) applied to female mouse skin]

Tris(2-chloroethyl)phosphate (TCEP), a widely used flame retardant, was tested for its skin chronic toxicity/carcinogenicity using female Slc: ddY mice. TCEP (5 and 50%) dissolved in ethanol was applied to the shaved skin twice a week for 79 weeks. The control group received ethanol under similar condition. In addition, 5 animals in each group were killed at 6 and 12 months and used for the chronic toxicity study. In body weight, food consumption and survival rate, there was no significant difference between the control and treated groups. Spleen weight was decreased in the 50% group. No significant difference in the incidence of tumors and other non-neoplastic lesions of the skin and other organs was found between the control and treated groups. The results indicate that under the conditions of the present study, TCEP has no carcinogenicity and toxicity for the skin.

Plasma renin activity in shock due to aluminium phosphide poisoning

Plasma renin activity (PRA) was estimated in 30 patients with aluminium phosphide (AIP) poisoning (study group) admitted in shock. Ten patients in shock other than due to AIP poisoning (Group II A) and 20 normal healthy subjects (Group II B) served as controls. The PRA was significantly higher in the study group and group II A as compared to normal healthy subjects (p less than 0.001). Significantly higher PRA was found in the study group as compared to Group II A (p less than 0.001). The initial higher PRA continued to rise further in the study group but it started decreasing in Group II A as the duration of shock advanced. Continuation of shock in AIP poisoning was probably due to slow release of toxic PH3 gas, which was detected by positive silver nitrate paper test. The rise in PRA was directly proportional to the dose of pesticide consumed. There was direct relationship of mortality with increased PRA. Angiotensin converting enzyme inhibitors may have a role in combating shock in AIp poisoning.

Conditioned taste aversion in lesser bandicoot rat, Bandicota bengalensis

The lesser bandicoot rat after ingesting a sublethal dose of 0.025% zinc phosphide, in preferred food millet (Pennisetum typhoides) grains, for 4 days, showed aversion for 5-6 days towards plain millet offered in choice with the less preferred sorghum (Sorghum vulgare) grains. The aversion response to nontoxic bait was stronger (aversion index greater than 0.7) for first 3-4 days in individual and for 1-2 days in paired rats. 100% or more shift in aversion index from pre-treatment to post-treatment periods indicated that the aversive and naive partners of the heterosexual and unisexual female pairs mutually influence the feeding preferences of each other as a result of which they showed aversion for first 2-3 days to the plain food in which poison was given to one of the partner earlier.

Myocardial perfusion imaging with 99mTc-DMPE in man

Technetium-99m DMPE (99mTc-DMPE) is a newly synthesized myocardial perfusion imaging agent that shows intense myocardial accumulation in the dog. In the present study, dosimetry and potential clinical usefulness of this agent were assessed in four human subjects. Absorbed radiation doses were low, with the highest doses consisting of 200 mrad/mCi (54 microGy/MBq) to the gallbladder and 160 mrad/mCi (43 microGy/MBq) to the liver. No evidence of clinical toxicity was found. Technetium-99m DMPE did image the myocardium, but the ratio of target to nontarget activity was less favorable than that observed in the dog. Intense hepatic 99mTc-DMPE activity interfered with clinical imaging of the cardiac apex in two of the four subjects. We conclude that the prototype radiopharmaceutical, 99mTc-DMPE, is capable of myocardial perfusion imaging in man but the planar myocardial images produced are of inferior quality compared with 201Tl myocardial images. Further work is justified to develop related compounds to overcome the clinical limitations described.

An oral formulation of gold for the treatment of rheumatoid arthritis

Twenty-two patients with active rheumatoid arthritis were entered into a trial during which an oral gold formulation was administered at two dosages (4 mg/d and 6 mg/d) for 12 weeks. Seventeen patients completed the trial. Both dosages produced a similar improvement in the indices of inflammation. Five patients were not benefited by the treatment, adverse side-effects were reported in 10 and 5 were withdrawn from the trial.

Other penicillamine-like drugs

Drugs like penicillamine act slowly, benefit extraarticular features of the disease as well as the joints, reduce erythrocyte sedimentation rate and rheumatoid factor titer and may slow the progression of radiographic changes and alter the outcome of the disease. Their action is to some extent disease-dependent. The 1st choice of drugs of this type is now penicillamine. It compares favourably with other drugs of the same type including gold, azathioprine and levamisole. A number of compounds in the development stage offer potential advantages over currently available drugs of this class. A compound which was safe enough to be recommended for widespread use would take over the role of first-line treatment of rheumatoid arthritis.

Pharmacokinetics of gold following administration of auranofin (SK+FD-39162) and myochrysine to rats

Auranofin orally administered to rats resulted in delayed and protracted peak blood and serum gold levels occurring 24 to 48 h post administration. During this period, the gold concentration in blood was higher than in serum indicating that a major portion of gold was associated with the cellular components. During 1st order elimination (greater than 48 h), the blood/serum gold ratio decreased which suggested dissociation of cellular gold. Biliary cannulation experiments demonstrated that the protracted gold levels (24 to 48 h) could not be due to hepatic recirculation. In contrast to auranofin, gold sodium thiomalate produced blood gold levels which peaked within 3 h, rapidly declined and were consistently lower than serum gold levels.

Studies of the intestinal metabolism of oral gold

In order to understand some of the unique toxic/therapeutic properties of the orally administered gold containing compound auranofin, the intestinal metabolism of gold was studied in 4 normal subjects. A triple lumen intestinal perfusion apparatus was used to measure intestinal flux using a non-absorbable radiolabelled marker dilution technique. Over a short (50 cm) segment of proximal small bowel, substantial disappearance of gold was observed; the findings, however, were most consistent with a loose, reversible adsorption onto the enteric cell surface rather than true trans-mucosal absorption. There was no evidence for an entero-hepatic recirculation of gold in these subjects or in 4 additional patients with rheumatoid arthritis studied in a similar manner.

Oral chrysotherapy in rheumatoid arthritis: minimum effective dose

We studied the dose-response to a new oral gold compound in 28 patients with definite rheumatoid arthritis, divided in 4 groups of 7 patients, each treated with different doses of auranofin for 3 months. Clinical and laboratory parameters were recorded weekly, and blood gold levels (BGL) measured by atomic absorption spectroscopy. Six and 9 mg daily doses of auranofin were most effective based on clinical and laboratory results. Correlation studies between BGL and percent decrease of humoral measurements, within the 3 months were statistically were statistically significant. Mean BGL, associated with clinical improvement, reached 0.73 microgram/ml, and was accompanied by a 17.6% decrease from initial value of IgG, 17.1% of alpha 2-globulin, 48.9% of RF titer and 25.9% of ESR.

A comparative field trial, conducted without pre-treatment census baiting, of the rodenticides zinc phosphide, thallium sulphate and gophacide against Rattus norvegicus

The effectiveness of the single-dose poison treatments of farm rat infestations, analysed by comparing the weights of the post-treatment census bait takes in covariance with the weights of the prebait takes, showed that treatments with 2-5% zinc phosphide, 0-3% thallium sulphate or 0-3% gophacide were equally effective and significantly better than were treatments with 1% zinc phosphide or 0-1% thallium sulphate. The methodology and sensitivity of different analyses are also considered.

Acute and subacute inhalation toxicities of phosphine, phenylphosphine and triphenylphosphine

The four-hour LC50 values for ChR-CD male rats for phosphine, phenylphosphine and triphenylphosphine have been determined to be 0.44 micromoles per liter (muM/liter), 1.56 muM/liter and 47.8 muM/liter respectively. The dose-death curves are parallel. During exposure, all three caused clinical signs indicative of mild respiratory irritation. Triphenylphosphine also caused severe weight loss immediately after exposure, followed by normal rate of weight gain. No histopathologic effects due to exposure were seen in any of the tissues examined after single exposures to any of the three compounds. Phosphine and triphenylphosphine caused mild weight loss during a 10-day exposure period followed by normal rate of weight gain during a 14-day recovery period. The phenylphosphine exposures caused a decreased rate of weight gain during the exposure period which returned to normal during the recovery period. Silver nitrate paper was found to be unsuitable for field analysis of phenylphosphine.