A critical review of the toxicology of glutaraldehyde.

Glutaraldehyde, a low molecular weight aldehyde, has been investigated for toxicity in humans and animals. Examination of this dialdehyde was indicated from previous studies with other aldehydes in which carcinogenicity of formaldehyde and toxicity of acetaldehyde and malonaldehyde have been disclosed. Information gaps concerning the actions of glutaraldehyde have been identified in this review and recommendations are suggested for additional short- and long-term studies. In particular, information regarding irritation of the respiratory tract, potential neurotoxicity, and developmental effects would assist in a complete hazard evaluation of glutaraldehyde. Further study related to disposition, metabolism, and reactions of glutaraldehyde may elucidate the mechanism of action.

Membrane flow within the myelin sheath in IDPN neuropathy.

This report describes some aspects of beta,beta'-iminodipropionitrile (IDPN) neuropathy in rats as observed by ultrastructural methods and X-ray diffraction. Light microscopy shows gross swelling of the axons in proximal lumbar spinal roots 8 days after intraperitoneal injection of IDPN. Mean axon cross-sectional area and mean axon perimeter increased to 280% and 160% of their control values, respectively. At the same time, myelin membrane packing was not visibly disturbed. In addition, X-ray diffraction patterns, recorded under physiological conditions, demonstrate that the myelin lipid bilayer thickness and widths of the aqueous spaces between bilayers did not change. Related observations are made on posterior tibial nerve (PNS myelin) and ventral spinal cord (CNS myelin). The various observations together are interpreted in terms of a fluid myelin membrane. It is proposed that the myelin membrane flows during axon swelling even though normal membrane-membrane contacts are maintained within the sheath. Membrane flow and slippage between membranes are explained in terms of a molecular model of the myelin multilayer.

Evaluation of the genotoxic potential of glutaraldehyde.

The cytotoxic and genotoxic effects of glutaraldehyde were studied in vitro in the human TK6 lymphoblast cell line and in primary cultures of rat hepatocytes. TK6 lymphoblasts were exposed to glutaraldehyde for 2 hr in serum-free GSH-free media. Cytotoxic effects were observed at concentrations as low as 10 microM with only 10% cell survival at 20 microM. Alkaline elution studies indicated that glutaraldehyde-induced DNA-protein crosslinking increased linearly over the concentration range from 0 to 25 microM. Glutaraldehyde-induced mutations were assessed at the thymidine kinase locus over the same concentration range and reached a plateau at 10 microM of about six times the background mutant frequency. At equivalent levels of DNA-protein crosslinks and cytolethality, glutaraldehyde was mutagenic at approximately a one-seventh lower concentration than the rodent nasal carcinogen formaldehyde (Craft et al.; Mutation Research 176:147-155, 1987). Glutaraldehyde induced a marginal increase in unscheduled DNA synthesis in the in vitro hepatocyte DNA repair assay, but only at the two highest concentrations of 50 and 100 microM, indicating the induction of some DNA excision-repair activity. These data demonstrate that glutaraldehyde exhibits DNA-reactive genotoxic activity that may involve, at least in part, DNA-protein crosslinking in these cell culture models. These findings suggest the need to examine the potential carcinogenic activity of glutaraldehyde in appropriate inhalation studies.

Ecological toxicology and human health effects of heptachlor.

The chlorinated cyclodiene heptachlor was registered in 1952 as an agricultural and domestic insecticide. By early 1984, registration for all purposes, except subterranean termite control and for limited use in the control of fire ants, had been cancelled. This restriction of use arose primarily from concerns over the environmental persistance and bioaccumulation potential of the organochlorine pesticides. Currently, sale of heptachlor has been voluntarily suspended over questions about its carcinogenic potential, and the absence of safe and effective application methods. As a persistent organochlorine pesticide, heptachlor residues are detected in all components of the environment. In historical use, heptachlor was directly applied to terrestrial systems, while air and water were secondarily contaminated via volatilization and land run-off, respectively. Within each environmental compartment, heptachlor undergoes a variety of metabolic and abiotic transformations. In vivo studies indicate that heptachlor epoxide is the predominant metabolite, formed as a product of the mixed-function oxidase system, while 1-hydroxychlordene is the major soil metabolite. For quantification, heptachlor and its metabolites are extracted from air, soil and sediment, water, or biological materials using various organic solvents and analyzed by gas chromatography or thin-layer chromatography. Residue reports comprise most of the literature concerning the effects of heptachlor on the biota. In many such reports, toxic effects cannot be conclusively attributed to heptachlor exposure. Toxicity to organisms seems more dependent on acute exposure, while the chronic effects of low level exposure to heptachlor are poorly defined. Maximal terrestrial residues coincide with temporal and spatial proximity to application; peak residues in aquatic systems on the other hand, correlate to periods of maximum run-off. The lipophilic nature of both heptachlor and heptachlor epoxide results in the potential for significant bioaccumulation in all lipid-type compartments in the environment. The toxic effects of heptachlor are not specific for any one organ system. The liver and the central nervous system are most significantly affected by heptachlor, although effects can also be seen in the reproductive, hematopoietic, immune, and renal systems. An important consideration is the relation of relevant environmental exposure levels to toxicity. The concentrations necessary to elicit results in laboratory experiments do not translate directly to the same results upon environmental exposure, nor do experimental laboratory animal models absolutely equate with native-state organisms or with humans.(ABSTRACT TRUNCATED AT 400 WORDS)

Pathology and cell proliferation induced by intra-nasal instillation of aldehydes in the rat: comparison of glutaraldehyde and formaldehyde.

The relative toxicities of formaldehyde and glutaraldehyde to the rat nasal epithelium were determined following intra-nasal instillation of aqueous solutions of these compounds into one nostril of male Fischer 344 (F-344) rats. Lesions identical in appearance to those resulting from acute inhalation exposure to formaldehyde were induced by both compounds in a concentration-dependent manner. Treatments included India ink or 1 M methylene blue (for instillation deposition studies); sterile saline (vehicle control); 40, 200, 400, and 800 mM formaldehyde; and 10, 20, and 40 mM glutaraldehyde. Dye-treated rats were sacrificed immediately, and nasal passages were examined to determine the localization of instilled materials. Three days after treatment, all other animals received a single ip injection of 5-bromo-2'-deoxyuridine 2 hr prior to sacrifice, and the nasal passages were prepared for histopathology and cell proliferation studies. While sterile saline and 10 mM glutaraldehyde induced no significant epithelial changes, 20 and 40 mM glutaraldehyde induced extensive lesions in the treated side of the nose. Aldehyde-induced lesions included inflammation, epithelial degeneration, respiratory epithelial hypertrophy, and squamous metaplasia in association with marked increases (3-8-fold) in labeling index for both compounds. Formaldehyde induced similar lesions but required concentrations of 200 mM or more to elicit a toxic response. Thus, glutaraldehyde is approximately an order of magnitude more toxic to the nasal epithelium than formaldehyde. These studies also indicate that the nose is very resistant to the aldehydes studied, requiring instillation of millimolar concentrations before toxic responses occurred.

Sural nerve biopsy in chronic inflammatory demyelinating polyradiculoneuropathy.

We compared histologic features of sural nerve biopsies in 14 patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) with those in other forms of neuropathy. In CIDP endoneurial pericapillary cellular infiltrates were found in 4 patients (29%), onion bulbs in 5 patients (36%), and predominant demyelination in 7 patients (50%). None of these abnormalities was specific, but cellular infiltrates and onion bulbs appear to be diagnostically useful when combined with clinical information. To detect macrophage infiltration of myelin, cell nuclei were counter-stained in 20 teased fiber preparations. Nine patients with CIDP had a significantly higher mean number of cells per centimeter of teased fiber than 11 patients with other neuropathies. Despite overlap, significant infiltration of myelin detected by this method suggests CIDP in an appropriate clinical setting.

Neurofilament protein crosslinking in gamma-diketone neuropathy: in vitro and in vivo studies using the seaworm myxicola infundibulum.

Neurofilament (NF) protein crosslinking has been proposed as the ultimate pathogenetic mechanism underlying the neuropathies caused by the gamma-diketones 2,5-hexanedione (HD) and 3,4-dimethyl-2,5-hexanedione (DMHD). Mammalian models have been used to investigate this hypothesis, but alternative experimental models are needed. Myxicola infundibulum is a marine worm which is gaining popularity in neuroscience research because of its large syncytial axon. A model system using Myxicola has been developed to investigate NF crosslinking in worms exposed to neurotoxic agents whose putative mechanisms involve covalent crosslinking of NF proteins. In vitro studies using purified NF demonstrate that progressive alkylation of Myxicola NF with [2,5-14C]DMHD is accompanied by NF protein crosslinking. Rabbit anti-Myxicola NF antisera showed highly restricted activity for Myxicola axoplasm and NF and were employed for immunoblotting axoplasm from Myxicola treated in vivo with DMHD. A dramatic increase in high molecular weight material was demonstrated in the axoplasm of treated worms, as demonstrated by polyacrylamide gel electrophoresis, and the new high molecular weight bands stained with the anti-NF antisera, indicating the presence of anti-NF reactive material in the crosslinked protein. Further, there was progression of crosslinking after cessation of exposure in vivo, an observation which suggests oxidation of remaining pyrrolyl derivatives. These studies support previous observations which suggest that NF crosslinking is the molecular event which initiates NF aggregation in gamma-diketone neurotoxicity, and establish Myxicola infundibulum as a useful species in which to study certain neurotoxic compounds.

Pyrrole oxidation and protein cross-linking as necessary steps in the development of gamma-diketone neuropathy.

It has been well documented that the gamma-diketone HD1 is the ultimate toxic metabolite of n-hexane. Furthermore, it has been shown that the pathogenetic mechanism by which HD exerts its neurotoxic effects is through binding to protein lysly residues and cyclization to pyrroles. The present study sought to determine whether the presence of pyrrole residues on NF1 proteins is sufficient to cause the NF-filled axonal swellings associated with n-hexane and other gamma-diketone neuropathies or whether pyrrole oxidation and protein cross-linking also have to occur in order for neurotoxicity to develop. We synthesized the HD analogue AcHD1 and assessed its rate of pyrrole formation in vitro, the ease of oxidation of its resulting pyrroles, and its ability to cross-link proteins in vitro. The in vivo effects of AcHD on rats were examined following daily ip1 injections. AcHD was found to have a rate of pyrrole formation comparable to that of the potent HD analogue DMHD1 at 35 degrees C. The pyrrole derived from AcHD was more resistant to oxidation than that derived from the neurotoxic compound HD. AcHD did not cross-link proteins in vitro. Pyrrole derivatives were demonstrated on hemoglobin isolated from animals treated with HD, DMHD, and AcHD. Cross-linked spectrin was detected in animals treated with HD and DMHD but not with AcHD. Rats receiving 0.1 or 0.25 mmol of AcHD/kg/day did not reach the end point of hindlimb paralysis observed in the gamma-diketone neuropathies, and the NF-filled axonal swellings seen following exposure to the neurotoxic gamma-diketones were not observed.(ABSTRACT TRUNCATED AT 250 WORDS)