Contact hypersensitivity to stainless steel cages (chromium metal) in hairless descendants of mexican hairless dogs

Metal reactivity is present in dogs with tibial plateau leveling osteotomy and total hip replacement implants

OBJECTIVE

Determine whether dogs with well-functioning orthopedic metal implants can develop metal reactivity.

SAMPLE

Client-owned dogs that had tibial plateau leveling osteotomy (TPLO) or total hip replacement (THR) implants for 12 months or more and control dogs with no implants.

PROCEDURES

Lymphocyte transformation testing was performed by exposing peripheral blood lymphocytes to nickel (Ni), chromium (Cr), cobalt (Co), or a combination of these metals. Lymphocyte proliferation was assessed with flow cytometry. Lymphocyte stimulation indexes (SIs) were calculated. A SI > 2 was considered reactive. Median SIs of dogs in response to metal exposure were compared statistically.

RESULTS

Samples from 10 dogs with TPLO, 12 dogs with THR, and 7 control dogs were analyzed. Six dogs out of 22 with metal implants had a reactive SI to 1 or more metals, while 2 of 7 control dogs had a SI > 2 when exposed to nickel only. When all metals were considered, no differences in metal reactivity were found between TPLO, THR, and control groups.

CLINICAL RELEVANCE

Metal reactivity is present in dogs and can be identified using lymphocyte transformation testing. Reactivity to Ni is present in dogs with and without metal implants. Reactivity to Co and Cr occurs in some dogs with metal implants.

Assessment of immunotoxicity in female Fischer 344/N and Sprague Dawley rats and female B6C3F1 mice exposed to hexavalent chromium via the drinking water

Sodium dichromate dihydrate (SDD), an inorganic compound containing hexavalent chromium (Cr(VI)), is a common environmental contaminant of groundwater sources due to widespread industrial use. There are indications in the literature that Cr(VI) may induce immunotoxic effects following dermal exposure, including acting as both an irritant and a sensitizer; however, the potential immunomodulatory effects of Cr(VI) following oral exposure are relatively unknown. Following the detection of Cr(VI) in drinking water sources, the National Toxicology Program (NTP) conducted extensive evaluations of the toxicity and carcinogenicity of SDD following drinking water exposure, including studies to assess the potential for Cr(VI) to modulate immune function. For the immunotoxicity assessments, female Fischer 344/N (F344/N) and Sprague Dawley (SD) rats and female B₆C₃F₁ mice were exposed to SDD in drinking water for 28 consecutive days and evaluated for alterations in cellular and humoral immune function as well as innate immunity. Rats were exposed to concentrations of 0, 14.3, 57.3, 172, or 516 ppm SDD while mice were exposed to concentrations of 0, 15.6, 31.3, 62.5, 125, or 250 ppm SDD. Final mean body weight and body weight gain were decreased relative to controls in 250 ppm B₆C₃F₁ mice and 516 ppm SD rats. Water consumption was significantly decreased in F344/N and SD rats exposed to 172 and 516 ppm SDD; this was attributed to poor palatability of the SDD drinking water solutions. Several red blood cell-specific parameters were significantly (5-7%) decreased in 250 ppm mice; however, these parameters were unaffected in rats. Sporadic increases in the spleen IgM antibody response to sheep red blood cells (SRBC) were observed, however, these increases were not dose-dependent and were not reproducible. No significant effects were observed in the other immunological parameters evaluated. Overall, exposure to Cr(VI) in drinking water had limited effects on the immune system in both rats and mice.

Contact dermatitis caused by sunless tanning treatment with dihydroxyacetone in hairless descendants of Mexican hairless dogs

Dihydroxyacetone (DHAT) is a color additive that is added to sunless tanning products to produce an artificial tan. Although this agent has been used extensively as safe sunless tanning, no published data are available to judge whether the abuse of DHAT causes a potential hazard to the human skin. The purpose of this study was to clarify whether frequent treatment with DHAT solutions had a deleterious effect on the wide skin surface of hairless descendants of Mexican hairless dogs. The skin reactions to the DHAT-treatment were investigated by daily clinical observations and histopathological examinations (21 and 42 days after the beginning of the DHAT-treatment). Clinical observations showed that skin color changes were apparent within 6 h after the first treatment with 5% DHAT solutions, with maximal darkening between 12 and 24 h. Twenty-one days after the beginning of the treatment with 5% DHAT solutions, the skin developed irritant dermatitis, and then the skin lesions gradually became severe during this study. Histopathological examinations showed entire epidermal thickening, 21 days after the beginning of the treatment with 5% DHAT solutions. Forty-two days after the beginning of the treatment with 5% DHAT solutions, the skin exhibited remarkable epidermal degeneration (hyperplastic and dyskeratotic changes) and moderate inflammatory reactions in the dermis. In severe dermatitic sites, I found focal epidermal necrosis or interepidermal blister formation beneath the thickened parakeatotic corneum. Throughout this study, there were no clinical and histopathological changes in the sites treated with vehicle alone. These results revealed that the skin coloring generated by frequent wide treatments with DHAT caused severe contact dermatitis which was associated with the damaged stratum corneum.