Concentrations of Triiodothyronine and Thyroxine in Equine Fetal Serum during Gestation1

Allen, Andrew L.; Doige, C. E.; Haas, S D; Card, Claire; Fretz, P B

doi:10.1093/biolreprod/52.monograph_series1.49

Cited by 2 publications

(2 citation statements)

References 4 publications

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“…Serum concentrations of total thyroxine (T 4 ) and triiodothyronine (T 3 ) were measured (Allen et al, 1995;Rawlings et al, 1998) using a fluorescence polarization immunoassay (TDx Systems, Abbott Laboratories, Irving, TX). The limits of sensitivity were 5 nmol and 0.23 nmol/L, respectively.…”

Section: Hormone Assaysmentioning

confidence: 99%

Thyroid Function and Effects on Reproduction in Ewes Exposed to the Organochlorine Pesticides Lindane or Pentachlorophenol (Pcp) From Conception

Beard

Rawlings²

1999

Journal of Toxicology and Environmental Health, Part A

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There is concern over the potential endocrine-modulating effects of long-term exposure to pesticides. In this study, ewe lambs were exposed to lindane and pentachlorophenol (PCP) from conception to necropsy at 67 wk. of age. The ewe lambs (and their mothers) were given untreated feed (n = 6) or feed treated with 1 mg/kg body weight/day of lindane (n = 8) or PCP (n = 13). Estrus was synchronized at 32 wk. of age, and ewe lambs were exposed to vasectomized rams. Ewe lambs were then exposed to intact rams during the following two natural estrous periods and subsequent reproductive performance was monitored. Serum was collected every 2 wk. during development, daily during the synchronized cycle and frequently (every 15-60 min) for 6-18 h either with or without stimulation with thyroid-stimulating hormone (TSH) during the synchronized luteal phase or TSH/thyroid-releasing hormone (TRH) at 65-66 wk of age. Ewe lambs fed a PCP-treated diet had a significantly reduced serum concentration of both T4 and free T4, and a reduction in the magnitude and duration of the T4 and free T4 response to TSH, despite normal endogenous levels of TSH and a normal TSH response to TRH. PCP exposure had a less detrimental influence on unstimulated T3 levels; however, the T3 (but not reverse T3) response to TSH was markedly reduced in PCP-treated ewe lambs. Ewe lambs given lindane also had a significantly reduced serum concentration of T4; however, despite continued exposure to lindane, T4 levels returned to normal by 10 wk. of age. Detrimental effects on reproductive function were only seen following estrous synchronization when both PCP and lindane exposure reduced the number of corpora lutea (CL) and total CL volume and increased luteinizing hormone (LH) pulse frequency. In addition, lindane-treated ewes had shorter estrous cycles and lower luteal progesterone concentrations. No marked effects of pesticides were seen on fertility following mating during natural estrous periods. In conclusion, the pesticides affected reproduction only after estrous synchronization, whereas PCP consistently disrupted thyroid function, most likely through a direct effect on the thyroid gland.

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Section: Hormone Assaysmentioning

confidence: 99%

Thyroid Function and Effects on Reproduction in Ewes Exposed to the Organochlorine Pesticides Lindane or Pentachlorophenol (Pcp) From Conception

Beard

Rawlings²

1999

Journal of Toxicology and Environmental Health, Part A

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“…O momento durante o qual o hipotireoidismo ocorre vai determinar os sinais clínicos no potro, sendo incoordenação, reflexo de sucção fraco, hipotermia e desordens musculoesqueléticas os principais (IRVINE, 1984). Dentre as alterações musculoesqueléticas prognatismo, deformidades flexurais nos membros torácicos e pélvicos, ruptura do tendão extensor digital comum, ossificação anormal/ retardatária dos ossos do carpo e do tarso, deformidades angulares e articulações frouxas são as mais encontradas (ALLEN et al, 1995). Potros que passaram por tireoidectomia parcial in utero nasceram com pelagem imatura, fracos, incapazes de se manter em pé e apresentando atraso na maturação esquelética (ALLEN et al, 1998).…”

Section: Cortisolunclassified

>b<Efeito da suplementação hormonal com progestágenos em éguas prenhes sobre os hormônios tireoidianos e esteroides dos neonatos>/b<

Redoan¹

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Concentrations of Triiodothyronine and Thyroxine in Equine Fetal Serum during Gestation1

Cited by 2 publications

References 4 publications

Thyroid Function and Effects on Reproduction in Ewes Exposed to the Organochlorine Pesticides Lindane or Pentachlorophenol (Pcp) From Conception

Thyroid Function and Effects on Reproduction in Ewes Exposed to the Organochlorine Pesticides Lindane or Pentachlorophenol (Pcp) From Conception

>b<Efeito da suplementação hormonal com progestágenos em éguas prenhes sobre os hormônios tireoidianos e esteroides dos neonatos>/b<

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