Evaluation of the safety of sodium pectate as a food ingredient.

New potential uses of pectates in food products have recently stimulated interest in re-evaluating the information available concerning the safety of pectins and pectates as food ingredients. Data relevant to this re-evaluation have been obtained in rats in recent 14-day and 13 wk subchronic feeding studies with sodium pectate. Ames tests and other mutagenicity tests have been conducted with sodium pectate, bleached sodium pectate and mixed sodium/calcium pectate salts. These toxicological studies with pectates have provided further evidence of their safety, and support of the continued GRAS status of pectins and pectate salts.

Teratological evaluation of FD&C Red no. 2-a collaborative government -industry study. III. IBT's study.

Because of recent studies indicating possible embryolethality and teratogenicity of FD&C Red No.2, an ad hoc committee was convened by the Food and Drug Administration to consider these questions. The committee suggested a collaborative study by three laboratories [Food and Drug Administration (FDA), Industrial Bio- Test Laboratories (IBT), and National Center for Toxicological Research (NCTR)] in which Red No. 2 was given at 200 mg/kg body weight, by gavage during dose level via water bottle. Appropriate controls were utilized. FDA used Osborne-Mendel stran rats, IBT used Charles River, and NCTR used both strains. No significant increases in skeletal or visceral abnormalities were seen. No significant increase in resorptions was seen in the Osborne-Mendel strain, but the Charles River stain at IBT showed a significant increase in litters with two or more resorptions after dams had been given 200 mg/kg at 0-19 days of gestation. The NCTR study on the Charles River strain also showed an increase in the same parameter for the same dose level and in addition showed a significant increase in the percentage of resorptions per litter. It was concluded that because of the inherent variation and the absence of an increase in abnormalities or other indications of embryotoxicity, there is reason to doubt that this effect is either biologically significant or reproducible.

Thyroid function and thyroid tumors in toxaphene-treated rats.

Historically, a direct and irreversible genotoxic reaction of a xenobiotic with DNA has been considered to be a universal and obligatory initiating event in the etiology of neoplasia, and it was assumed therefore that (1) there was no threshold other than zero exposure for cancer initiation, and (2) like radiation, exposure was additive over a lifetime. Human exposure to xenobiotics causing neoplasia in laboratory rodents has been regulated in many countries on that basis. In the last decade evidence has accumulated indicating that some neoplasia in laboratory rodents may not be caused by a direct and irreversible interaction of xenobiotics with DNA. In addition, it has been found that some neoplasia caused in laboratory rodents by xenobiotics may not be relevant for biochemical/physiological reasons. This has raised the question whether human exposure to these xenobiotics should be regulated by the no-threshold philosophy used for direct-acting genotoxic xenobiotics or whether they can be regulated by the threshold philosophy used for classical xenobiotic-induced toxic effects. In a bioassay carried out by the National Cancer Institute and published in 1979, toxaphene was found to cause an increase in the occurrence of two spontaneously occurring tumors in laboratory rodents that since have been found to have both genotoxic and nongenotoxic etiologies in laboratory rodents. Experiments described in this paper are part of a program to help elucidate whether the increased incidence of these two neoplasms in laboratory rodents could have had a nongenotoxic origin, and thus whether toxaphene could be regulated by a threshold approach. Forty male rats were orally intubated with 100 mg/kg/day technical grade toxaphene in corn oil for 3 days. The dose was reduced to 75 mg/ kg/day on Day 4 due to toxicity. This lower dose was administered daily for 25 days. Another group of 40 male rats was orally gavaged daily with equivalent volumes of corn oil. After 0, 7, 14, and 28 doses, 10 test and 10 vehicle control animals were sacrificed for gross and histopathological examination of thyroid, parathyroid, and pituitary glands. Weights of these endocrine organs, body weights, and brain weights were determined. Prior to sacrifice, a blood sample was obtained from each animal for preparation of serum for analyses of thyroid stimulating hormone (TSH), thyroxine (T4), thyroid hormone (T3), and reverse T3 (rT3). Thyroid glands were evaluated microscopically for follicular cell hypertrophy, hyperplasia, and colloid storage. There were significant time-related increases in serum TSH in the test animals after 7, 14, and 28 doses of toxaphene. The serum levels of T3, T4, rT3, and corrected T3 (CrT3) in the test group were not significantly different from controls at each interval. Thyroid gland weights and thyroid to brain weight ratios were not significantly (p > 0.05) increased in the test group at each sacrifice interval. Pituitary weight, brain weight, and the ratios of these organ weights to body weights were similar in the test and control groups at each sacrifice interval. Thyroid follicular cell hypertrophy and intrafollicular hyperplasia increased and thyroid follicular cell colloid stores decreased with duration of treatment with toxaphene. The hormonal and histopathologic changes seen in the test group were consistent with increased excretion of T3 and/or T4 resulting from cytochrome P450 enzyme induction in the liver. This mechanism for thyroid neoplasia is not known to occur in humans.

Investigation of hepatic cytochrome P-450 enzyme induction and DNA adduct formation in male CD/1 mice following oral administration of toxaphene.

Exposure of experimental animals to toxaphene induces hepatic cytochrome P-450 (CYP). Although chronic administration of toxaphene to mice was found to cause an increased incidence of liver tumors, a mechanism for its carcinogenicity has yet to be elucidated. We investigated two potential mechanisms of toxaphene-induced carcinogenicity: peroxisomal proliferation and DNA binding. Peroxisomal proliferation was evaluated by measuring the level of immunodetectable CYP 4A1, an isozyme of CYP that is specifically induced by peroxisomal proliferators, in hepatic microsomes from CD1 mice that were treated by oral gavage for seven consecutive days with corn oil vehicle or 10, 25, 50 or 100 mg kg(-1) toxaphene. In comparison to control mice, toxaphene-treated mice had increased liver weight, increased liver/body weight ratios and increased levels of total hepatic CYP and cytochrome b5. No increase in the level of immunodetectable levels of CYP 4A1 was found in hepatic microsomes from toxaphene-treated mice when compared to controls. In contrast, increases in immunodetectable CYP 4A1 were detected in hepatic microsomes from mice treated with the peroxisomal proliferator clofibrate. These findings suggest that toxaphene-induced induction of CYP may not involve CYP 4A1 and that peroxisomal proliferation may not be involved in toxicity. Significant increases in immunodetectable levels of CYP 2B were, however, detected in toxaphene-treated mice, and are consistent with earlier reports demonstrating that toxaphene, like many other pesticides, induces the phenobarbital-inducible subfamily of CYP. Analysis of DNA adduct levels in the livers of toxaphene-treated mice by DNA 32P-post-labeling showed no evidence of DNA adduct formation.

A new approach to the safety assessment of pharmaceutical excipients. The Safety Committee of the International Pharmaceutical Excipients Council.

This article presents a set of proposed guidelines for the safety assessment of new pharmaceutical excipients. These guidelines were developed by the Safety Committee of the International Pharmaceutical Excipients Council and represent a new, scientifically based approach to establishing conditions for the safe use of proposed pharmaceutical excipients utilizing various routes of human exposure. They are based upon the best currently available toxicological science and have taken the deliberations of the International Conference on Harmonization into consideration. These guidelines were developed because there are no regulatory agency guidelines currently available which specifically address the toxicological testing of a material intended for use as an excipient in pharmaceutical preparations. Only materials which have been previously permitted for use in a pharmaceutical preparation or which have been permitted for use in foods may be considered safe under current practices. If implemented, these guidelines should expedite the review of a proposed new excipient by regulatory agencies.