The effect of flight, fasting and p,p′-DDT on thyroid hormones and corticosterone in Gambel's white-crowned sparrow, Zonotrichia leucophrys gambelli

Edward J. Scollon, James A. Carr, George P. Cobb

Research output: Contribution to journalArticle

27 Scopus citations

Abstract

This study examined the effects of p,p′- dichlorodiphenyltrichloroethane (p,p′-DDT), fasting and flight on thyroid hormones and corticosterone in Gambel's White-crowned Sparrows (Zonotrichia leucophrys gambelli). Female sparrows were dosed daily with either 5 mg p,p′-DDT per kg body mass or corn oil vehicle over 3 days. On the fifth day the sparrows were divided into 3 groups: (1) unstressed - non-stressed control sparrows; (2) fasted - sparrows fasted for intervals ranging from 20 min to 9 h; or (3) flown - sparrows flown in a wind tunnel for intervals between 20 min and 2.5 h while fasting. Half the sparrows from each group received DDT (DDT-dosed sparrows) and the other half corn oil vehicle only (vehicle sparrows). Trunk blood plasma was analyzed for thyroxine, triiodothyronine and corticosterone using radioimmunoassay. In the flown group, corticosterone was elevated (DDT-dosed 35.52 ng/ml, P≤0.05), and thyroxine was depressed (DDT-dosed 4.09 ng/ml, P≤0.05; vehicle 4.33 ng/ml, P≤0.05). Elevated corticosterone likely decreased thyroid hormone production through a negative feedback mechanism originating at the hypothalamus. Mean triiodothyronine concentrations did not differ among any of the test groups. Relative to time fasted and flown, thyroxine decreased in flown birds dosed with DDT (P<0.001) and triiodothyronine decreased in fasted birds dosed with DDT (P=0.004). The increased rate of hormone diminution may be a result of the ability of DDT to induce microsomal enzyme production.

Original languageEnglish
Pages (from-to)179-189
Number of pages11
JournalComparative Biochemistry and Physiology - C Toxicology and Pharmacology
Volume137
Issue number2
DOIs
StatePublished - Feb 2004

Keywords

  • Chromohelicase-DNA- binding (CHD) gene
  • Corticosterone
  • Fasting
  • Flight
  • Thyroxine
  • Triiodothyronine
  • White-crowned sparrow
  • Wind tunnel
  • p,p′-dichlorodiphenyltrichloroethane

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