Testosterone, corticosterone, and photoperiod interact to regulate plasma levels of binding globulin and free steroid hormone in Dark-eyed Juncos, Junco hyemalis

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Abstract

The pharmacology and regulation of corticosteroid binding globulins (CBG) in Dark-eyed Juncos, Junco hyemalis, was investigated. The equilibrium dissociation constant for [3H]corticosterone (CORT) binding to plasma was < 5 nM. This binding site had a similar high affinity for progesterone, approximately fivefold lower affinity for androgens, and negligible affinity for estradiol. The following data suggested that plasma CBG levels are regulated by both testosterone and day length: (1) CBG binding capacity in free-living adult males was greater in early than in late breeding season and greater in males than in females and (2) CBG levels were higher in testosterone-treated, castrated males than in castrated males receiving no testosterone and still higher in testosterone-treated males exposed to long days than in similar males exposed to short days. Birds apparently lack a sex steroid-specific binding globulin, but it was estimated that more than 90% of testosterone in junco plasma should bind to CBG. An increase in plasma CORT, such as occurs during a stress response, was judged to acutely increase free testosterone levels as much as fivefold. Corticosterone and testosterone may thus interact in a complex manner in species that lack sex hormone binding proteins.

Original languageEnglish (US)
Pages (from-to)67-77
Number of pages11
JournalGeneral and Comparative Endocrinology
Volume122
Issue number1
DOIs
StatePublished - 2001

Fingerprint

Junco
Junco hyemalis
Globulins
Photoperiod
steroid hormones
corticosterone
Corticosterone
Transcortin
globulins
testosterone
Testosterone
photoperiod
adrenal cortex hormones
Steroids
Hormones
sex hormones
Gonadal Steroid Hormones
binding capacity
pharmacology
androgens

Keywords

  • Androgen
  • Castration
  • CBG
  • Dark-Eyed Junco
  • Seasonality
  • Sex hormones
  • Transcortin

ASJC Scopus subject areas

  • Endocrinology

Cite this

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title = "Testosterone, corticosterone, and photoperiod interact to regulate plasma levels of binding globulin and free steroid hormone in Dark-eyed Juncos, Junco hyemalis",
abstract = "The pharmacology and regulation of corticosteroid binding globulins (CBG) in Dark-eyed Juncos, Junco hyemalis, was investigated. The equilibrium dissociation constant for [3H]corticosterone (CORT) binding to plasma was < 5 nM. This binding site had a similar high affinity for progesterone, approximately fivefold lower affinity for androgens, and negligible affinity for estradiol. The following data suggested that plasma CBG levels are regulated by both testosterone and day length: (1) CBG binding capacity in free-living adult males was greater in early than in late breeding season and greater in males than in females and (2) CBG levels were higher in testosterone-treated, castrated males than in castrated males receiving no testosterone and still higher in testosterone-treated males exposed to long days than in similar males exposed to short days. Birds apparently lack a sex steroid-specific binding globulin, but it was estimated that more than 90{\%} of testosterone in junco plasma should bind to CBG. An increase in plasma CORT, such as occurs during a stress response, was judged to acutely increase free testosterone levels as much as fivefold. Corticosterone and testosterone may thus interact in a complex manner in species that lack sex hormone binding proteins.",
keywords = "Androgen, Castration, CBG, Dark-Eyed Junco, Seasonality, Sex hormones, Transcortin",
author = "Pierre Deviche and Creagh Breuner and Miles Orchinik",
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T1 - Testosterone, corticosterone, and photoperiod interact to regulate plasma levels of binding globulin and free steroid hormone in Dark-eyed Juncos, Junco hyemalis

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AU - Breuner, Creagh

AU - Orchinik, Miles

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N2 - The pharmacology and regulation of corticosteroid binding globulins (CBG) in Dark-eyed Juncos, Junco hyemalis, was investigated. The equilibrium dissociation constant for [3H]corticosterone (CORT) binding to plasma was < 5 nM. This binding site had a similar high affinity for progesterone, approximately fivefold lower affinity for androgens, and negligible affinity for estradiol. The following data suggested that plasma CBG levels are regulated by both testosterone and day length: (1) CBG binding capacity in free-living adult males was greater in early than in late breeding season and greater in males than in females and (2) CBG levels were higher in testosterone-treated, castrated males than in castrated males receiving no testosterone and still higher in testosterone-treated males exposed to long days than in similar males exposed to short days. Birds apparently lack a sex steroid-specific binding globulin, but it was estimated that more than 90% of testosterone in junco plasma should bind to CBG. An increase in plasma CORT, such as occurs during a stress response, was judged to acutely increase free testosterone levels as much as fivefold. Corticosterone and testosterone may thus interact in a complex manner in species that lack sex hormone binding proteins.

AB - The pharmacology and regulation of corticosteroid binding globulins (CBG) in Dark-eyed Juncos, Junco hyemalis, was investigated. The equilibrium dissociation constant for [3H]corticosterone (CORT) binding to plasma was < 5 nM. This binding site had a similar high affinity for progesterone, approximately fivefold lower affinity for androgens, and negligible affinity for estradiol. The following data suggested that plasma CBG levels are regulated by both testosterone and day length: (1) CBG binding capacity in free-living adult males was greater in early than in late breeding season and greater in males than in females and (2) CBG levels were higher in testosterone-treated, castrated males than in castrated males receiving no testosterone and still higher in testosterone-treated males exposed to long days than in similar males exposed to short days. Birds apparently lack a sex steroid-specific binding globulin, but it was estimated that more than 90% of testosterone in junco plasma should bind to CBG. An increase in plasma CORT, such as occurs during a stress response, was judged to acutely increase free testosterone levels as much as fivefold. Corticosterone and testosterone may thus interact in a complex manner in species that lack sex hormone binding proteins.

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