Testosterone, Corticosterone, and Photoperiod Interact to Regulate Plasma Levels of Binding Globulin and Free Steroid Hormone in Dark-Eyed Juncos, Junco hyemalis

Deviche, Pierre; Breuner, Creagh W.; Orchinik, Miles

doi:10.1006/gcen.2001.7613

Cited by 133 publications

(85 citation statements)

References 51 publications

(77 reference statements)

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“…So while less CORT may be immediately available to target cells, increased CBG capacity would presumably decrease the metabolic clearance rate of CORT. In many species, the binding capacity of CBG is far greater than the concentration of total CORT in plasma, although this is not always the case (Deviche et al 2001). If the CBG is present in concentrations far in excess of steroid, then small changes in the fraction of CBG occupied could have a large effect on the amount of free vs bound CORT.…”

Section: Cbg Diversitymentioning

confidence: 99%

“…4). Despite the lower affinity for CBG, Deviche et al (2001) estimated that 90% of testosterone was bound to CBG at baseline levels of CORT. Hence, CBG is a physiologically relevant androgen binding globulin, and may play a role in regulating free testosterone levels during development and adulthood.…”

Section: Androgen Binding Globulin?mentioning

confidence: 99%

“…In fact, in many avian studies, CBG capacity is greater when testosterone is naturally elevated (i.e. the breeding season: Romero & Wingfield (1998), Romero et al (1998b,c), Deviche et al (2001)) and experimentally elevated (i.e. via testosterone implant: Klukowski et al (1997), Deviche et al (2001)).…”

Section: Androgen Binding Globulin?mentioning

confidence: 99%

“…the breeding season: Romero & Wingfield (1998), Romero et al (1998b,c), Deviche et al (2001)) and experimentally elevated (i.e. via testosterone implant: Klukowski et al (1997), Deviche et al (2001)). These data suggest that a primary function of CBG during the breeding season may be to regulate free testosterone.…”

Section: Androgen Binding Globulin?mentioning

confidence: 99%

“…However, if the animal becomes stressed, total CORT levels can increase 5-fold, and should displace testosterone from CBG (due to the higher affinity for CORT). Therefore, an increase of CORT in response to stress will cause a surge in free testosterone (Deviche et al 2001;Fig. 5).…”

Section: Androgen Binding Globulin?mentioning

confidence: 99%

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Plasma binding proteins as mediators of corticosteroid action in vertebrates

Breuner

Orchinik

2002

Journal of Endocrinology

419

247

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Stressors elicit a complex but variable suite of endocrine events. Comparative studies of the stress response have focused primarily on the adrenocortical response to stress, in particular the measurement of plasma levels of glucocorticoids. However, a number of other factors contribute to and modify cellular and organismal responses to glucocorticoids. Notably, plasma corticosteroid binding globulins (CBGs) can regulate the general availability of steroid to tissues, and/or direct the delivery of hormones to specific sites. In this paper, we discuss possible functions of CBG and mechanisms of CBG action, review CBG characteristics among vertebrates, and discuss our recent studies indicating that CBG may indeed modulate responses to stressors. For example, in house sparrows, we found that basal and stress-induced concentrations of total corticosteroid (cortisol or corticosterone) (CORT) vary seasonally, but CBG concentrations change proportionally, so that free CORT concentrations appear static yearround. In contrast, in white-crowned sparrows and tree lizards, CBG concentrations change under conditions when total CORT levels do not, resulting in significant changes in circulating free CORT. These differences in free CORT are masked if CBG is not accounted for. We have also found that the binding properties of CBG vary considerably between species and need to be determined empirically. Such studies led to the observation that CBG in several species may also serve as a functional androgen binding protein; this is especially important for birds, because previous studies had concluded that birds lack androgen binding globulins. We propose that consideration of CBG is paramount to understanding the role of glucocorticoids in mediating behavioral and physiological responses to stress.

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Section: Cbg Diversitymentioning

confidence: 99%

Section: Androgen Binding Globulin?mentioning

confidence: 99%

Section: Androgen Binding Globulin?mentioning

confidence: 99%

Section: Androgen Binding Globulin?mentioning

confidence: 99%

Section: Androgen Binding Globulin?mentioning

confidence: 99%

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Plasma binding proteins as mediators of corticosteroid action in vertebrates

Breuner

Orchinik

2002

Journal of Endocrinology

419

247

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Regulation of male traits by testosterone: implications for the evolution of vertebrate life histories

Hau¹

2007

BioEssays

511

350

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The negative co-variation of life-history traits such as fecundity and lifespan across species suggests the existence of ubiquitous trade-offs. Mechanistically, trade-offs result from the need to differentially allocate limited resources to traits like reproduction versus self-maintenance, with selection favoring the evolution of optimal allocation mechanism. Here I discuss the physiological (endocrine) mechanisms that underlie optimal allocation rules and how such rules evolve. The hormone testosterone may mediate life-history trade-offs due to its pleiotropic actions in male vertebrates. Conservation in the actions of testosterone in vertebrates has prompted the 'evolutionary constraint hypothesis,' which assumes that testosterone signaling mechanisms and male traits evolve as a unit. This hypothesis implies that the actions of testosterone are similar across sexes and species, and only the levels of circulating testosterone concentrations change during evolution. In contrast, the 'evolutionary potential hypothesis' proposes that testosterone signaling mechanisms and male traits evolve independently. In the latter scenario, the linkage between hormone and traits itself can be shaped by selection, leading to variation in trade-off functions. I will review recent case studies supporting the evolutionary potential hypothesis and suggest micro-evolutionary experiments to unravel the mechanistic basis of life-history evolution.

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Variation in corticosterone response and corticosteroid binding‐globulin during different breeding sub‐stages in Eurasian tree sparrow (Passer montanus)

Sun

et al. 2015

J. Exp. Zool.

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In free-living animals, it has been well demonstrated that the intensity of the adrenocortical response to acute restraint stress can vary with reproductive investment during breeding. The parental care hypothesis posits that the stress response is negatively correlated with parental investment in avian species. To further test this hypothesis, we examined changes in both free and total corticosterone (CORT) at baseline and stress-induced levels (maximal CORT) and corticosteroid-binding globulin (CBG) capacities, in both sexes of a multi-brooded Eurasian tree sparrows (Passer montanus), during the nest building, the early nestling, the later egg-laying, and the later nestling stages. Our results showed Eurasian tree sparrows did not exhibit any differences between sexes in CORT and CBG levels during the egg-laying or nestling stages. Both sexes had lowered CBG capacities and females exhibited lower maximal CORT during the early compared to later nestling stages. In addition, both sexes had lower maximal free CORT levels during the nest building stage than those of the early nestling stages, and males expressed higher total maximal CORT levels than females during nest building stage. The variation in CORT response and CBG levels during different breeding sub-stages in Eurasian tree sparrow may correlate with their energetic situations and parental investments. J. Exp. Zool. 325A:75-83, 2016. © 2015 Wiley Periodicals, Inc.

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Testosterone, Corticosterone, and Photoperiod Interact to Regulate Plasma Levels of Binding Globulin and Free Steroid Hormone in Dark-Eyed Juncos, Junco hyemalis

Cited by 133 publications

References 51 publications

Plasma binding proteins as mediators of corticosteroid action in vertebrates

Plasma binding proteins as mediators of corticosteroid action in vertebrates

Regulation of male traits by testosterone: implications for the evolution of vertebrate life histories

Variation in corticosterone response and corticosteroid binding‐globulin during different breeding sub‐stages in Eurasian tree sparrow (Passer montanus)

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