Developmental toxicity of indium chloride by intravenous or oral administration in rats

Role of pH on indium bioaccumulation by Chlamydomonas reinhardtii

For divalent metals, the Biotic Ligand Model (BLM) has been proven to be an effective tool to predict biological effects by taking into account speciation calculations and competitive interactions. Nonetheless, the BLM has only rarely been validated for trivalent metals (e.g. rare earth elements), and the potential competitive effects of protons has been understudied. In this paper, the short-term biouptake of indium (In), a trivalent metal that is a byproduct of zinc extraction and used in numerous applications including the semiconductor industry, was evaluated under controlled conditions. Short-term (i.e. 60 min) indium biouptake by Chlamydomonas reinhardtii was measured as a function of pH in order to verify the validity of the BLM. At a given pH, In biouptake could be well described by the Michaelis-Menten equation with conditional stability constants of K_In,pH=4.0 = 10^6.7 M^-1, K_In,pH=5.0 = 10^8.6 M^-1, K_In,pH=6.0 = 10^9.3 M^-1 and maximum internalization fluxes of J_{max, pH=4.0} = 0.74 × 10^-14 mol cm^-2 s^-1, J_{max, pH=5.0} = 1.60 × 10^-14 mol cm^-2 s^-1, J_{max, pH=6.0} = 2.22 × 10^-14 mol cm^-2 s^-1. Although several potential mechanisms for the role of pH were examined, the results were best explained by a competitive interaction of H⁺ with the In uptake sites using overall stability constants of logK_In = 9.76 M^-1 and logK_H = 15.66 M^-1. Based on these results, pH will play a critical role in bioavailability measurements of the trivalent cations in natural waters.

Developmental toxicity of indium: embryotoxicity and teratogenicity in experimental animals

Indium, a precious metal classified in group 13 (IIIB) in the periodic table, has been used increasingly in the semiconductor industry. Because indium is a rare metal, technology for indium recycling from transparent conducting films for liquid crystal displays is desired, and its safety evaluation is becoming increasingly necessary. The developmental toxicity of indium in experimental animals was summarized. The intravenous or oral administration of indium to pregnant animals causes growth inhibition and the death of embryos in hamsters, rats, and mice. The intravenous administration of indium to pregnant animals causes embryonic or fetal malformation, mainly involving digit and tail deformities, in hamsters and rats. The oral administration of indium also induces fetal malformation in rats and rabbits, but requires higher doses. No teratogenicity has been observed in mice. Caudal hypoplasia, probably due to excessive cell loss by increased apoptosis in the tailbud, in the early postimplantation stage was considered to account for indium-induced tail malformation as a possible pathogenetic mechanism. Findings from in vitro experiments indicated that the embryotoxicity of indium could have direct effects on the conceptuses. Toxicokinetic studies showed that the embryonic exposure concentration was more critical than the exposure time regarding the embryotoxicity of indium. It is considered from these findings that the risk of the developmental toxicity of indium in humans is low, unless an accidentally high level of exposure or unknown toxic interaction occurs because of possible human exposure routes and levels (i.e. oral, very low-level exposure).

In vivo distribution and fractionation of indium in rats after subcutaneous and oral administration of [114mIn]InAs

Two in vivo experiments were carried out in this study. In the first experiment five rats were given two subcutaneous injections of [(114m)In]InAs. Major sites of accumulation were spleen, liver and kidney. The intracellular distribution of indium was examined by differential centrifugation. The cytoplasmic fraction contained most of the indium activity followed by the mitochondrial fraction. Both outcomes are in close agreement with the results obtained in previous studies. Chromatographic separations on a preparative size exclusion column were carried out. It was shown that indium was mostly bound to high molecular mass compounds in serum and in the cytoplasmic fraction of spleen, liver and kidney. In a second experiment five rats were given four oral doses of [(114m)In]InAs over a short period. Prior to this experiment the in vitro solubility of cold InAs in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) was determined using graphite furnace atomic absorption spectroscopy. In the case of the SGF only 1.3% of an InAs suspension dissolved after 48 hours incubation at 37 degrees C. InAs was not soluble in SIF. Uptake of InAs after oral administration was minimal (<1%). Due to incomplete removal of traces of [(114m)In]InAs from the gastrointestinal tract, it was impossible to calculate accurately the in vivo distribution over the different organs. As the uptake and consequently the activity in the organs were very low, no further chromatographic separations could be carried out. Considering this very low uptake, it can be concluded that InAs will not accumulate in the body after oral exposure.

Hemodynamic effect of indium chloride in pregnant rats

Daily indium chloride doses of control (0) or 200 mg/kg were administered orally to pregnant Sprague-Dawley (SD) rats by gavage, on d 6-15 of gestation. On d 16 of gestation hemodynamic tests were performed; Arterial blood pressure, cardiac output (CO), and volume organ blood flow were determined with radioactive microspheres using the reference sample method (McDevitt & Nies, 1976). Indium chloride increased the cardiac index (CI), but did not change arterial blood pressure and total peripheral resistance (TPR). Indium decreased the organ fractions of the cardiac output to kidneys, ovaries, uterus, and placenta, while those to brain, lungs, and liver were not affected. In the placenta the blood flow was reduced significantly while the vascular resistance increased. The blood flow and vascular resistance did not change in the rest of the organs studied. The changes in arterial blood pressure, CO, Cl, TPR, organ fraction of cardiac output, blood flow, and vascular resistance in most of the organs displayed normal responsiveness to noradrenaline (NA) infusion. The reduction of uterine and placenta fractions and placental blood flow, produced by NA infusion were significantly greater in control than in the indium-treated group. Data indicate that the hemodynamic changes induced by indium are detrimental to the fetus. Indium chloride exposure modifies the maternal effect of noradrenaline such that there is maternal survival at the expense of fetal mortality.

Radioactivity in breast milk following 111In-octreotide

The concentration of 111In in breast milk in a 10 weeks postpartum woman was measured at daily intervals up to 72 h post-injection of 5.3 mCi (196 MBq) of 111In-octreotide (OctreoScan). Radiation surveys were also performed at the breast surface. The disappearance of 111In from the breast milk exhibited a bi-exponential pattern with a maximum concentration of 14.2 nCi (0.54 kBq) per 125 ml feeding at 4 h, with lower values thereafter. External surveys at the breast surface also showed a bi-exponential decrease with time. The maximum reading was 8.3 mrem x h(-1) (0.83 mSv x h(-1)) immediately after administration. This rapidly decreased due to 85% urinary excretion by 24 h. Breast milk tracer content and external surveys at the breast surface were determined at 3 h intervals for up to 10 days. If a newborn is nursed for the first 10 days, the internal and external dose equivalents would be 22.97 mrem (0.23 mSv) and 27.86 mrem (0.28 mSv), respectively, for a total of 50.83 mrem (0.5 mSv). The patient was instructed to resume breast-feeding on day 10, when the newborn received a total dose equivalent of 1.55 mrem (0.016 mSv). This dosimetry is based on a very conservative assumption, whereby 100% of the ingested 111In becomes systemic and follows adult bio-behaviour. Oral indium has been shown to be poorly absorbed from the gastrointestinal tract (approximately 0.15%), which suggests the infant's dose could be considerably less. Based on this case report, mathematical relationships are presented for determining the nursing infant's dose equivalent from internal and external exposures relative to time after the maternal administration of 111In-octreotide (OctreoScan).

Developmental toxicity of indium in cultured rat embryos

Developmental toxicity of indium was examined using rat embryo culture with reference to toxicokinetics. Rat embryos at day 9.5 of pregnancy were cultured for 48 h under various exposure conditions to indium trichloride. Indium was embryotoxic to cultured rat embryos at concentrations ranging from 25 to 50 microM for 24 h exposure according to the embryonic age, and the exposure concentration was more critical than the exposure time. The embryotoxic concentrations were comparable to the serum concentration at a developmentally toxic dose by intravenous administration in an in vivo experiment. It was considered from these results that the developmental toxicity of indium is a direct effect on the embryo or yolk sac and that weak developmental toxicity of indium by oral administration was due to low exposure concentrations in the embryo.