Increased corticosteroid binding capacity of plasma albumin but not of corticosteroid-binding globulin caused by ACTH-induced changes in free fatty acid concentrations in snowshoe hares and rabbits

Boonstra, Rudy; Tinnikov, Alexander A.

doi:10.1677/joe.0.1560205

Cited by 22 publications

(15 citation statements)

References 30 publications

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“…() found a major temporary increase in the maximum corticosteroid‐binding capacity of blood within 30 min following an ACTH injection in wild snowshoe hares. A similar increase was shown in laboratory rabbits (Boonstra & Tinnikov ). By selective degradation of CBG, Boonstra & Tinnikov () showed that the increased CORT binding was entirely owing to changes in the binding properties of albumin, not to changes in CBG binding.…”

Section: Corticosteroid‐binding Globulinsupporting

confidence: 85%

“…A similar increase was shown in laboratory rabbits (Boonstra & Tinnikov ). By selective degradation of CBG, Boonstra & Tinnikov () showed that the increased CORT binding was entirely owing to changes in the binding properties of albumin, not to changes in CBG binding.…”

Section: Corticosteroid‐binding Globulinsupporting

confidence: 85%

“…However, there may be variation among species in the response to a stressor. Thus, for example, ACTH is sufficient to mobilize FFA in lagomorphs (Desbals, Desbals & Agid ; Boonstra & Tinnikov ), whereas in rodents, both ACTH and CORT are needed (Baggen et al . ).…”

Section: What Happens Next: Downstream Measures Of Chronic Stressmentioning

confidence: 99%

“…Evidence : Free fatty acids have been found to decline with chronic stress in some studies on natural populations of birds and mammals (Boonstra et al . ; Clinchy et al . ), but more comprehensive measurement of FFA is warranted.…”

Section: What Happens Next: Downstream Measures Of Chronic Stressmentioning

confidence: 99%

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Evaluating stress in natural populations of vertebrates: total CORT is not good enough

2012

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Summary1. Our goal in this review is to discuss how measures beyond simple quantification of total glucocorticoid levels are needed in comparative studies of stress. We need to measure corticosteroid binding globulin -CBG -and further downstream performance metrics to properly evaluate the significance and impact of stress in wild populations. We briefly cover the current literature, discuss methods that may enable detection of chronic stress and point to directions for future research to continue to clarify this field. 2. CBG may regulate access of hormones to tissues, but disagreement remains as to the functional importance of total vs. free vs. bound hormone in the plasma. Here we focus on recent studies providing solid evidence supporting the free hormone hypothesis. These studies unequivocally indicate that the biologically active fraction consists only of the portion that is free (not total levels in the blood). We also present the 'reservoir hormone hypothesis', indicating the relevance of CBG-bound hormone in the plasma. 3. The vast majority of physiological studies on stress in natural populations only measure blood corticosterone or its faecal metabolites. However, downstream metrics (e.g. immune function, oxidative stress and body mass changes) can assess the physiological impact of the changes in corticosterone and CBG and ultimately of the adaptiveness of these changes. Here we will discuss some of the most promising factors that can be measured downstream of the plasma and the rationale for their measurement, how to do it, and an introduction to the evidence. 4. Although we draw on biomedical findings for some of this insight, we recognized that findings from a few mammalian laboratory species (primarily rats and mice) may not apply to the vast diversity of vertebrate species from fish to birds. In large measure we are still in the natural history phase of the accumulation of fundamental knowledge in terms of trying to extract general principles in the stress biology of natural populations. Our review outlines what is needed to lay the foundation for these principles.

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Section: Corticosteroid‐binding Globulinsupporting

confidence: 85%

Section: Corticosteroid‐binding Globulinsupporting

confidence: 85%

Section: What Happens Next: Downstream Measures Of Chronic Stressmentioning

confidence: 99%

Section: What Happens Next: Downstream Measures Of Chronic Stressmentioning

confidence: 99%

See 2 more Smart Citations

Evaluating stress in natural populations of vertebrates: total CORT is not good enough

2012

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“…(7), while the other did not (18). Because hypoxia induces hyperlipidemia in suckling rats (26) and hyperlipidemia alters the serum binding of corticosterone (4,13), we repeated these measurements after delipidation of serum using Lipoclear (Statspin, Norwood, MA).…”

Section: Acth Injection and Blood And Tissue Samplingmentioning

confidence: 99%

Adrenocortical responses to ACTH in neonatal rats: effect of hypoxia from birth on corticosterone, StAR, and PBR

Raff

Hong

Oaks

et al. 2003

American Journal of Physiology-Regulatory, Integrative and Comp

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The adrenocortical response to hypoxia may be a critical component of the adaptation to this common neonatal stress. Little is known about adrenal function in vivo in hypoxic neonates. The purpose of this study was to evaluate adrenocortical responses to ACTH in suckling rat pups exposed to hypoxia from birth to 5-7 days of age compared with normoxic controls. We also evaluated potential cellular controllers of steroidogenic function in situ. In 7-day-old pups at 0800, hypoxia from birth resulted in increased basal (12.2 Ϯ 1.4 ng/ml; n ϭ 12) and ACTHstimulated (94.0 Ϯ 9.4 ng/ml; n ϭ 14) corticosterone levels compared with normoxic controls (basal ϭ 8.3 Ϯ 0.5 ng/ml; n ϭ 11; stimulated ϭ 51.3 Ϯ 3.8 ng/ml; n ϭ 8). This augmentation occurred despite no significant difference in plasma ACTH levels in normoxic vs. hypoxic pups before (85 Ϯ 4 vs. 78 Ϯ 8 pg/ml) or after (481 Ϯ 73 vs. 498 Ϯ 52 pg/ml) porcine ACTH injection (20 g/kg). This effect was similar in the afternoon at 6 days of age and even greater at 5 days of age at 0800. The aldosterone response to ACTH was not augmented by exposure to hypoxia from birth. Adrenocortical hypoxia-inducible factor (HIF)-1␣ mRNA was undetectable by RT-PCR. Steroidogenic acute regulatory (StAR) protein in adrenal subcapsules (zona fasciculata/reticularis) was augmented by exposure to hypoxia; this effect was greatest at 5 days of age. Peripheral-type benzodiazepine receptor (PBR) protein was also increased at 6 and 7 days of age in pups exposed to hypoxia from birth. We conclude that hypoxia from birth results in an augmentation of the corticosterone but not aldosterone response to ACTH. This effect appears to be mediated at least in part by an increase in controllers of mitochondrial cholesterol transport (StAR and PBR) and to occur independently of measurable changes in endogenous plasma ACTH. The augmentation of the corticosterone response to acute increases in ACTH in hypoxic pups is likely to be an important component of the overall physiological adaptation to hypoxia in the neonate. adrenocorticotropin; aldosterone; newborn; steroidogenic acute regulatory protein; peripheral-type benzodiazepine receptor; hypoxia-inducible factor HYPOXIA is one of the most common causes of neonatal morbidity and mortality (10, 17). Considerable attention has been paid to the short-and long-term neurological, cardiopulmonary, and renal consequences of neonatal hypoxia (3,8,14,34,36). In comparison, the adrenal adaptation in vivo to prolonged neonatal hypoxia has not been extensively studied. One pertinent study in human infants with hypoxemia due to bronchiolitis demonstrated an augmented cortisol, but not aldosterone, response to ACTH (12). This suggests a zone-specific adrenal adaptation to hypoxia.We have extensively examined dispersed adrenal cells in vitro removed from suckling rats exposed to hypoxia from birth (28). We have found that, as opposed to adult rats (29), steroidogenesis in vitro is augmented in adrenal cells from hypoxic neonatal rats despite no changes in steroidogenic enzy...

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Contrasting stress response of male Arctic ground squirrels and red squirrels

Boonstra

McColl

2000

J. Exp. Zool.

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A hormonal‐challenge protocol was used to compare the stress response of males of Arctic ground squirrels and red squirrels during the breeding season (May). These squirrels live in the same boreal forest of the Yukon, but have very different life histories and utilize the forest in markedly different ways. Red squirrels had levels of total cortisol, maximum corticosteroid‐binding capacity, and free cortisol that were 5, 7, and 2 times, respectively, those of Arctic ground squirrels. Red squirrels were resistant to suppression by an artificial glucocorticoid, dexamethasone (DEX); Arctic ground squirrels were not. Cortisol levels in red squirrels responded slowly but continuously to the ACTH injection; Arctic ground squirrels responded rapidly and then stabilized. Testosterone levels in red squirrels were extremely sensitive to the challenge, being suppressed by both DEX and ACTH; levels in Arctic ground squirrels were resistant to the challenge, being modestly suppressed by DEX and stimulated by ACTH. Energy mobilization, as measured by glucose and free fatty acid responses, was not affected. Red squirrels had four times the levels of white blood cells and higher proportions of lymphocytes and lower proportions of eosinophils than Arctic ground squirrels, indicating that the latter were in worse condition immunologically. Our evidence suggests that the functions associated with the hypothalamic‐pituitary‐adrenal axis are compromised in breeding male Arctic ground squirrels, but not in red squirrels. We propose that in male red squirrels this axis has evolved in the context of a stable social system based on long‐lived animals with individual territories which are needed to deal with unpredictable winter food supplies. In contrast, Arctic ground squirrels escape the rigors of winter by hibernation and this hormonal axis has evolved in short‐lived males in the context of intense intra‐sexual competition in a social system based on female kin groups and regular male dispersal to avoid inbreeding. J. Exp. Zool. 286:390–404, 2000. © 2000 Wiley‐Liss, Inc.

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Increased corticosteroid binding capacity of plasma albumin but not of corticosteroid-binding globulin caused by ACTH-induced changes in free fatty acid concentrations in snowshoe hares and rabbits

Cited by 22 publications

References 30 publications

Evaluating stress in natural populations of vertebrates: total CORT is not good enough

Evaluating stress in natural populations of vertebrates: total CORT is not good enough

Adrenocortical responses to ACTH in neonatal rats: effect of hypoxia from birth on corticosterone, StAR, and PBR

Contrasting stress response of male Arctic ground squirrels and red squirrels

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