Effects of polychlorinated biphenyl (PCB) on regulation of thyroid-, growth-, and neurochemically related developmental processes in young rats

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:5519675

Juarez de Ku, L M

Neonatal exposure to the toxic chemical polychlorinated biphenyl (PCB) induces hypothyroidism and retarded growth. Neonatal rats made hypothyroid by chemical or surgical means experience retarded growth and subnormal activity of choline acetyltransferase (ChAT) This study compared thyroid-, growth-, and neurochemically-related processes altered by hypothyroidism induced by other means, with PCB-induced hypothyroidism: (1) titers of thyroid stimulating hormone (TSH); (2) titers of hormones that regulate growth [growth hormone (GH), insulin-growth like factor-I (IGF-1), growth hormone releasing hormone (GHRH) and somatostatin (SS)]; or (3) brain ChAT activity. Whether PCB-induced growth retardation and other alterations are secondary to accompanying hypothyroidism rather than or in addition to a direct effect of PCB was also examined. Pregnant rats were fed chow containing 0 (controls), 62.5, 125, or 250 ppm PCB (entering offspring through placenta and milk) throughout pregnancy and lactation. Neonates exposed to PCB displayed many alterations similar to those made hypothyroid by other means: depression of overall and skeletal growth, circulating by other means: depression of overall and skeletal growth, circulating T[sub 4] levels and ChAT activity, and no change in hypothalamic GHRH and SS concentrations. Differences included a paradoxical increase in circulating GH levels, and no significant alteration of circulation IGF-1 and TSH levels and pituitary GH and TSH levels (although trends were in the expected direction). Thus, PCB-induced hypothyroidism may partially cause altered skeletal growth, circulating GH and TSH concentrations, and ChAT activity. Both T[sub 4] and T[sub 3] injections returned circulating TSH and GH levels and pituitary TSH content toward control levels; T[sub 3] restored skeletal, but not overall growth; and T[sub 4] elevated ChAT activity.

• Research Organization: Bowling Green State Univ., OH (United States)
• OSTI ID: 5519675
• Country of Publication: United States
• Language: English

Related Subjects

560300* -- Chemicals Metabolism & Toxicology
570000 -- Health & Safety
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
99 GENERAL AND MISCELLANEOUS
ANIMAL GROWTH
ANIMALS
AROMATICS
BIOLOGICAL EFFECTS
CHLORINATED AROMATIC HYDROCARBONS
GROWTH
HALOGENATED AROMATIC HYDROCARBONS
HORMONES
MAGNETIC FIELD CONFIGURATIONS
MAGNETIC FIELD REVERSAL
MAMMALS
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
PEPTIDE HORMONES
POLYCHLORINATED BIPHENYLS
PROTEINS
RATS
RODENTS
THYROID HORMONES
VERTEBRATES