Teratogenicity of lithium in mice

Pathologic Effects of Purified Polybrominated Biphenyl Congeners in Rats

Young male rats were fed diets containing 0, 1, 10, or 100 ppm of Firemaster (FM) BP-6 for 30 days, and the effects were compared with those caused by feeding diets containing identical amounts of either 2, 2', 4, 4', 5, 5-hexabromobiphenyl (HBB) or 2, 3', 4, 4', 5, 5'-HBB, two of the congeners contained in FM BP-6. In addition, rats were fed diets containing 0, 1, or 10 ppm of 3, 3', 4, 4', 5, 5'-HBB, a congener not in FM BP-6 but used because it is strictly a 3-methylcholanthrene (MC)-type inducer of hepatic drug metabolizing enzymes. Feed efficiency and weight gains were reduced only by 3, 3', 4, 4', 5, 5'-HBB at 10 ppm. Hepatomegaly occurred in rats given any of the chemicals. Vacuolation and enlargement of hepatocytes were observed in rats fed diets containing FM BP-6 or any of the congeners but were most prominent with 3, 3', 4, 4', 5, 5-HBB. Proliferation of smooth endoplasmic reticulum (SER), decreased rough endoplasmic reticulum (RER), and increased fat droplets were seen in hepatocytes of rats given FM BP-6. Similar but less severe changes were seen with 2, 3', 4, 4', 5, 5-HBB or 2, 2', 4, 4', 5, 5-HBB. The latter chemical produced the least severe changes. Hepatocytes of rats fed 10 ppm 3, 3', 4, 4', 5, 5'-HBB had extensive proliferation and disorganization of RER, increased fat droplets, and some proliferation of SER. Thymic and splenic atrophy associated with cortical lymphocytic depletion were observed only in rats fed 3, 3', 4, 4', 5, 5-HBB. 3, 3', 4, 4', 5, 5-HBB, which is an MC-type inducer, was the most toxic congener among the congeners studied. Apparently, 2, 2', 4, 4', 5, 5-HBB, which is the major congener in FM BP-6 and a phenobarbital (PB)-type inducer, contributes little to its toxicity. FM BP-6, a mixed (MC and PB)-type inducer, is more toxic than either 2, 2', 4, 4', 5, 5-HBB or 2, 3', 4, 4', 5, 5-HBB. However, 2, 3', 4, 4', 5, 5-HBB, a mixed-type inducer, is more toxic than 2, 2', 4, 4', 5, 5-HBB. Toxicity of FM BP-6 can be mostly attributed to its congeners with MC-type induction capability.

Application of the Hydra Assay for Rapid Detection of Developmental Hazards

Adult hydra and artificial “embryos” composed of randomly reaggregated cells of dissociated hydra were exposed to test chemicals. The lowest concentration killing adult hydra became the numerator, and the lowest concentration disrupting development of “embryos” became the denominator of a ratio. This adult toxic (A) to developmentally toxic (D) or A/D ratio from hydra was compared to the A/D ratio calculated from published reports employing standard laboratory animals. Data from rodents were considered if both adult and developmental toxicities were consistent for: species, route, and duration of treatment and had a direct dose-response relationship indicating that the toxic manifestations were near the low end of a dose-response curve. The minimal expression of adult toxicity was usually loss in body weight, but developmental toxicity varied from abnormal development or death to reduced fetal weight. The hydra assay proved as effective as standard safety evaluations in rodents at detecting developmental hazards, i.e., substances capable of disrupting the conceptus at a small fraction of the minimal dose toxic to adults. It also was as effective as rodents in establishing that the majority of substances are capable of disrupting development of the conceptus only at doses also toxic to adults.

Pattern of Response of Intact Drosophila to Known Teratogens

Drosophila, as the test organism, was used to assess 17 chemicals. The teratogenic potential of 15 of these chemicals is well established from animal studies or human epidemiology. The test involves examination of adult flies following treatment during larval stages of development. Flies are examined for abnormal external morphology. The incidence of abnormalities in treated and control populations is compared using the Chi-square test. All 17 chemicals were active to varying degrees in the test system. Most chemicals produced a unique response yielding individual patterns of abnormalities. These results suggest that Drosophila may have the potential to become a valuable teratogen screen, but further, more rigorous examination–particularly with nonteratogens–is required.

An Analysis of the Hydra Assay's Applicability and Reliability as a Developmental Toxicity Prescreen

A large and diverse group of chemicals was evaluated in the Hydra assay, and the outcomes were compared with those of standard developmental toxicity evaluations using data from pregnant mammals. Hydra correctly identified each of the substances previously found by in vivo tests to be uniquely hazardous to in utero development. Its overall accuracy was over 90%, and all of its errors were false positives. The fact that these positives were indeed false could have been established subsequently by routine testing in mammals. In no instance did the assay indicate that a chemical was not uniquely hazardous to the conceptus when higher level tests indicated that it was, i.e., 0 false negatives. The possible areas for continued refinement of the assay and expansion of its scope of use as well as perceived problems and limitations are discussed in detail.

Mutagenicity, carcinogenicity and teratogenicity of lithium compounds

This paper reviews the information available concerning the mutagenic, teratogenic and carcinogenic effects of lithium. Such effects would be highly unlikely in an occupational setting but might be a risk to the considerable percentage of the population treated for manic-depressive disorders. It is concluded that lithium compounds have no significant clastogenic and, based on studies on microorganisms, only a doubtful mutagenic activity. Information on teratogenic effects is contradictory. While some observations in man and a few animal studies suggest that lithium in concentrations in the order of those given to patients may cause malformations, other observations do not support this claim and the risk with a carefully controlled therapy is probably small. Until more information becomes available from ongoing lithium data registries, it is probably prudent to exercise caution in treating pregnant women with lithium during the period of cardiac organogenesis. No information is available on cancer caused by treatment with lithium, and it is highly unlikely that lithium is carcinogenic.

Teratogenic effects of lithium in mice

The question of the teratogenicity of lithium carbonate was tested in two inbred strains of mice that are susceptible to teratogens. Strains 129 and A/J mice were treated with varying dosages of lithium carbonate on day 8, 9, or 10, and strain A/J mice were sequentially treated on days 11, 12, and 13 of gestation. Another group of mice of strain 129 were given lithium carbonate in drinking water throughout pregnancy. Levels of lithium were determined in mouse serum (and in brain) of mothers and their offspring with the purpose of comparing equivalent values in mice and in man. A baseline dosage of 0.8 mg of lithium carbonate was chosen, since this dose produced a serum lithium level of 0.8 meq/L, which is comparable to values of patients treated for manic-depressive illness. This baseline dosage or 2 and 4 times this amount did not prove teratogenic in strain 129 mice. However, 5.0 mg (200 mg/kg), which is one-half the LD50 value, caused 41% malformations. The baseline dosage did not cause malformations in strain A/J when given on day 11, 12, or 13 of gestation. Lithium carbonate given in the drinking water to strain 129 mice throughout pregnancy at a concentration that produces serum levels in mice consistent with human values was deleterious. The data suggest that whole or part of total litters were eliminated. The few survivors were apparently normal. Our results suggest that 6 times the therapeutic serum lithium level in humans is teratogenic in mice, as tested by acute experiments. Chronic treatment with a quantity of lithium that produces a serum level equivalent to that of human values is toxic to whole or part of the litters of mice.

Lithium chloride induces partial responsiveness to LPS in nonresponder B cells

The lipopolysaccharide (LPS)-nonresponder mouse strains C3H/HeJ, C57BL/10ScCR and C57BL/10ScN do not respond to LPS acting as a polyclonal B-cell activator, a mitogen, or an adjuvant. The genetic basis for the defective LPS response has been extensive studied in C3H/HeJ and C57BL/10ScCR mice, in which it was demonstrated that a single gene locus on chromosome 4 was responsible for LPS unresponsiveness. Lithium chloride, a potent inhibitor of adenylate cyclase, not only improved lymphocyte activity in a patient with adenosine deaminase deficiency but also enhanced the phytohaemagglutinin (PHA)-induced responses of normal human lymphocytes. Therefore, we investigated whether LiCl could restore LPS responsiveness in spleen cells of C3H/HeJ mice. We show here that LPS, in the presence of LiCl, induced polyclonal IgM and IgG antibody formation and DNA synthesis in C3H/HeJ mouse spleen cells in vitro. Moreover, LiCl (10 mM), which by itself is non-mitogenic, increased RNA synthesis in spleen cells from both LPS-nonresponder and high responders strains; in contrast, LPS failed to increase RNA synthesis in cells from such LPS-nonresponder strains as C3H/HeJ and B10ScCr mice.