Environmental polychlorinated biphenyls: Acute toxicity of landfill soil extract to female prepubertal rats

Abstract

Subsurface soil from a National Priorities List landfill containing about 2.5% polychlorinated biphenyls (PCBs) was extracted and the extract cleaned by Florisil slurry and alumina column chromatography. The refined extract contained 48 mg/mL PCB, mainly trichlorobiphenyls and tetrachlorobiphenyls, traces of polychlorinated naphthalenes, 125 micrograms/mL 2,2-bis-p-chlorophenyl-1,1-dichloroethylene (DDE), and low levels of chlorinated dibenzofurans. The refined extract was dissolved in corn oil and administered intraperitoneally to weanling (day 20) female rats on days 20 and 21; rats were terminated on day 22. Limited data indicated possible hematopoietic effects, including neutrophilia. There were no changes in relative uterus, kidney, or adrenal gland weights between total doses of 3 to 96 mg/kg total PCB. Relative liver weights increased significantly at 36 mg/kg and activities of P450s 1A1 (as ethoxyresorufin O-dealkylase) and 2B (as pentoxyresorufin O-dealkylase) increased at 12 mg/kg and plateaued at 36 (P450 1A1) or 48 (P450 2b) mg/kg. Serum total thyroxine (T4) declined significantly at doses of 36 mg/kg and greater; thyroid follicular epithelial cells were significantly larger within the same dose range, but the follicular colloid area decreased to less than 60% control values at 12 mg/kg and remained at this size through 72 mg/kg. Maximum mobilization of T4 apparently occurred at 12 mg/kg and attenuated measured declines in circulating levels. Even though a large proportion of proven and probable estrogenic chlorobiphenyls (CBs) were present, the lower amounts of more potent antiestrogenic aryl hydrocarbon (Ah) receptor agonists and/or decreased responsiveness because of low serum T4 levels may have antagonized the uterotropic response.

Responses of Prepubertal Female Rats to Environmental PCBs with High and Low Dioxin Equivalencies

“…Four 1-ml aliquots of soil extract were chromatographed separately over the adsorbent, eluting with 20 ml of hexane (Fraction 1); two subsequent 10-ml eluates (Fractions 2 and 3) were retained separately for analysis only. Gas chromatography with electron capture detection (GC-ECD) on a 60-m DB-5 capillary column, as described in Hansen et al (1995, was conducted for the initial and charcoal-refined soil extracts to determine the amount and profile of PCBs recovered and lost PCDDS and PCDFs could not be detected by these methods. The basic proportions of the major PCB components were not changed (Fig.…”

Comparative evaluation of hepatotoxic and nephrotoxic effects of aroclors 1221 and 1254 in female rats

“…Hansen et al, observed no toxic effects of PCBs on the kidney in weanling female rats. 20 Induction of cytochrome P450 enzymes by PCBs both in kidney and liver has been shown. 21,22 Histological alterations in kidney were observed after administration of A1254 at 25 mg/kg for a period of 10 and 15 weeks.…”

Stepping backward to improve assessment of PCB congener toxicities.

“…After acute (2-day) exposures, thyroidstimulating hormone (TSH) levels may increase up to 5-fold (38) and the thyroid follicles show typical responses (32,39) to TSH-stimulated mobilization of T4 (39)(40)(41). The follicular response (increased cell height and decreased colloid area) appears maximal at doses below those at which significant declines in serum T4 are seen (40,41).…”

“…The follicular response (increased cell height and decreased colloid area) appears maximal at doses below those at which significant declines in serum T4 are seen (40,41). Mobilization of stored T4 from the thyroid follicles at doses lower than or times prior to those causing significant UDPGT induction (17,38) can cause elevations in serum T4 (17,42,43); at higher doses, declines in serum T4 are still seen at times prior to maximal UDPGT induction (17,38,42,43).…”