Toxicology and Humoral Immunity Assessment of Decamethylcyclopentasiloxane (D5) Following a 1-Month Whole Body Inhalation Exposure in Fischer 344 Rats

• DOI: 10.1093/toxsci/43.1.28
• Publication Date: 2007-01-13T13:41:31Z
• Authors: Leigh Ann Burns-Naas; Richard W. Mast; Paal C. Klykken; J. Ann McCay; Kimber L. White; Peter C. Mann; Dennis J. Naas
• Keywords: Immunotoxicology; Histopathology; Hematology; Beagle; Inhalation exposure

D5 is a low-molecular-weight cyclic siloxane used for industrial and consumer product applications. The objective of the present study was to assess potential toxic immunomodulatory consequences inhalation exposure D5. Male female Fischer 344 rats (25/group) were exposed by whole body 0, 10, 25, 75, or 160 ppm 6 h/day, 7 days/week 28 days. Clinical signs, weights, food consumption recorded. On day following final exposure, 10 rats/group/sex euthanized complete necropsy performed. Following 14-day nonexposure recovery period, remaining 5 rats/sex/group necropsied. Body organ weights obtained set tissues taken histopathology. Samples also collected serum chemistry, hematology, urinalysis. Immunotoxicology-designated (10/sex/group) immunized with sheep erythrocytes (sRBC) 4 days prior euthanasia cyclophosphamide (CYP) administered i.p. positive controls on 24 through 28. anti-sRBC antibody-forming cell (AFC) response evaluated in standard plaque assay. Blood examination enzyme-linked immunosorbant assay (ELISA). did not modulate humoral immunity, while internal control, CYP, produced expected suppression AFC response. caused no adverse effects weight, consumption, urinalysis parameters. Serum alkaline phosphatase (SAP) significantly decreased females at terminal (12%, ppm) sacrifice. A significant increase liver-to-body weight ratio observed animals end exposures (13%, ppm), but noted from same group. In males, increases (5%) thymus-to-body (14%) ratios high dose sacrifice recovery. At only, spleen-to-body (14 17%; 25 ppm, respectively) noted. histopathological analysis indicated an increased incidence severity nasal (Level 1) goblet proliferation. Focal macrophage accumulation lung be both sexes ppm. these organs appeared reversible. summary, alter immunity only minor, transient changes hematological, values. Histopathological confined respiratory tract effect level systemic toxicity, based primarily liver changes, 75