Chronic exposure to a low dose of ingested petroleum disrupts corticosterone receptor signalling in a tissue-specific manner in the house sparrow (Passer domesticus).

C R Lattin,L M Romero

doi:10.1093/conphys/cou058

Abstract

Stress-induced concentrations of glucocorticoid hormones (including corticosterone, CORT) can be suppressed by chronic exposure to a low dose of ingested petroleum. However, endocrine-disrupting chemicals could interfere with CORT signalling beyond the disruption of hormone titres, including effects on receptors in different target tissues. In this study, we examined the effects of 6 weeks of exposure to a petroleum-laced diet (1% oil weight:food weight) on tissue mass and intracellular CORT receptors in liver, fat, muscle and kidney (metabolic tissues), spleen (an immune tissue) and testes (a reproductive tissue). In the laboratory, male house sparrows were fed either a 1% weathered crude oil (n = 12) or a control diet (n = 12); glucocorticoid receptors and mineralocorticoid receptors were quantified using radioligand binding assays. In oil-exposed birds, glucocorticoid receptors were lower in one metabolic tissue (liver), higher in another metabolic tissue (fat) and unchanged in four other tissues (kidney, muscle, spleen and testes) compared with control birds. We saw no differences in mineralocorticoid receptors between groups. We also saw a trend towards reduced mass of the testes in oil-exposed birds compared with controls, but no differences in fat, kidney, liver, muscle or spleen mass between the two groups. This is the first study to examine the effects of petroleum on CORT receptor density in more than one or two target tissues. Given that a chronic low dose of ingested petroleum can affect stress-induced CORT titres as well as receptor density, this demonstrates that oil can act at multiple levels to disrupt an animal's response to environmental stressors. This also highlights the potential usefulness of the stress response as a bioindicator of chronic crude oil exposure.

Highlights

Cite as: Lattin CR, Romero LM (2014) Chronic exposure to a low dose of ingested petroleum disrupts corticosterone receptor signalling in a tissue-specific manner in the house sparrow (Passer domesticus)
This is despite the fact that changes in glucocorticoid titres may be a useful bioindicator of chronic exposure to a variety of toxicants, from heavy metals (Norris, 2000; Franceschini et al, 2009; Wada et al, 2009) to polychlorinated biphenyls (Love et al, 2003; Franceschini et al, 2008; Iwanowicz et al, 2009) to the focus of this study, crude oil (Rattner and Eastin, 1981; Gorsline and Holmes, 1982)
We examined the effects of a chronic low dose of ingested petroleum on CORT receptors

Summary

Introduction

Even though glucocorticoids are very important in helping individuals to cope with environmental challenges, endocrine disruption of the HPA axis is generally understudied (Hinson and Raven, 2006) This is despite the fact that changes in glucocorticoid titres may be a useful bioindicator of chronic exposure to a variety of toxicants, from heavy metals (Norris, 2000; Franceschini et al, 2009; Wada et al, 2009) to polychlorinated biphenyls (Love et al, 2003; Franceschini et al, 2008; Iwanowicz et al, 2009) to the focus of this study, crude oil (Rattner and Eastin, 1981; Gorsline and Holmes, 1982). There are several ways in which endocrine-disrupting chemicals could interfere with CORT signalling in addition to disrupting hormone synthesis and secretion; these include affecting target cell uptake, receptor activation and binding to the promoters of target genes (Odermatt et al, 2006)

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