The benefits of baseline glucocorticoid measurements: Maximal cortisol production under baseline conditions revealed in male Richardon’s ground squirrels (Urocitellus richardsonii) (original) (raw)
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Cortisol and corticosterone independence in cortisol-dominant wildlife
General and Comparative Endocrinology, 2012
Species have traditionally been defined as cortisol-dominant or corticosterone-dominant, depending on the glucocorticoid that is reported. To assess the degree of covariance versus independence between cortisol and corticosterone, 245 serum samples belonging to 219 individuals from 18 cortisol-dominant, non-domesticated species (6 mammalian orders) were compared by mass spectrometry. In these samples, which were elevated above baseline, concentration ranges were overlapping for cortisol and corticosterone although cortisol was dominant in every sample except one of 17 bighorn sheep with a corticosterone-biased cortisol-to-corticosterone ratio of 0.17. As expected, cortisol and corticosterone were strongly associated among species (r 2 = 0.8; species with high absolute cortisol tend to have high absolute corticosterone concentrations), with wide variation in the species-average cortisol-tocorticosterone ratio (range 7.5-49) and an even wider ratio range across individuals (0.2-341). However, only 9 out of 13 species with >7 individuals showed a positive association between cortisol and corticosterone among individuals, and repeated measures of the cortisol-to-corticosterone ratio within individuals were weakly associated (CV range 3-136%). We conclude that corticosterone, although at lower concentrations, has the potential to signal independently of cortisol, and should be included in integrated endocrine models of stress responses.
Journal of experimental zoology. Part A, Ecological genetics and physiology, 2013
Habitat can constrain and shape successful ecological and physiological strategies, thus providing the context for the evolution of life-history traits. However, unpredictable challenges, such as storms, natural disasters, and human activities can also have great effects on stress. Glucocorticoids (GCs) are adrenal steroid hormones that play an important role in how vertebrates cope with these predictable and unpredictable environmental challenges. Although assessing GCs levels can have many applications in the study of wildlife and/or captive animals, with or without capturing individuals, it requires a species-specific complete validation (analytical and biological) before its use. In this work, our aim was to: (a) validate a radioimmunoassay (RIA) for measuring GCs levels in L. guanicoe serum; (b) assess cortisol and corticosterone levels (if present) in serum of wild L. guanicoe individuals; and (c) compare the response to acute stressors (handling, shearing, and release). Our results successfully: (a) validated RIA for asses GCs levels in wild ungulates; (b) confirmed the presence for cortisol and corticosterone and showed that both GCs are differently affected by environmental stimuli in L. guanicoe; and (c) showed that GCs exhibit different patterns in the field and in response to acute stressors, making these camelids an interesting endocrinological model when seeking the adaptive functions of a given variation and further emphasizing the complexity of GC physiology in wild mammals.
General and Comparative Endocrinology, 2018
Southern flying squirrels have higher circulating cortisol levels than most vertebrates. However, regulation of tissue exposure to cortisol by the hormone's carrier protein, corticosteroid-binding globulin (CBG), appears to be altered due to lower-than-expected CBG expression levels, and a reduced affinity for cortisol. To assess the capacity of flying squirrels to regulate acute stress-mediated cortisol levels, we used the dexamethasone (DEX) suppression test followed by the adrenocorticotropic hormone (ACTH) stimulation test in both the breeding and non-breeding seasons, and quantified resultant changes in plasma cortisol and relative CBG levels. Regulation of cortisol via negative feedback, and the acute stress response appeared to function as they do in other vertebrates during the breeding season, but response to DEX in the non-breeding season showed that the sensitivity of the negative feedback mechanism changed across seasons. The relatively high concentrations of DEX required to induce negative feedback suggests that southern flying squirrels have a reduced sensitivity to cortisol compared with other vertebrates, and that high circulating cortisol levels may be required to compensate for low target tissue responsiveness in this species. Cortisol, but not CBG levels, were higher during the non-breeding than breeding season, and females had higher cortisol and CBG levels than males. Our data suggest that flying squirrel cortisol levels are regulated by negative feedback at a higher set point than in related species. Seasonal changes in cortisol levels, target tissue sensitivity to DEX, and in the capacity to respond to stressors appear to be part of the underlying physiology of southern flying squirrels, and may be required to maximize fitness in the face of tradeoffs between survival and reproduction.
General and Comparative Endocrinology, 2014
Across vertebrates, the hypothalamic-pituitary-adrenal axis is a conserved neuroendocrine network that responds to changing environments and involves the release of glucocorticoids into the blood. Few studies have been carried out concerning mammalian adrenal regulation in wild species either in the laboratory or field, and even fewer have been able to determine true glucocorticoid baselines. We studied the South-American caviomorph rodent Octodon degus, a diurnal and social mammal that has become an important species in the biological research. First, we determined the plasma cortisol baseline and the acute stress concentrations during the non-reproductive and mating seasons in free-living individuals. Second, using the same protocol we assessed the impact of long-term captivity on the adrenal function in wild-caught degus and degus born in laboratory. Third, we examined laboratory groups formed with degus taken from two distant natural populations; one of them originally occurs at the Andes Mountains in high altitude conditions. The data revealed seasonal modulation of basal cortisol in the wild associated with mating. In laboratory, degus presented higher cortisol stress responses, with greater magnitudes shown in degus born and reared in captivity. No differences between populations were found. The results suggest differential regulatory mechanisms between basal and stress-induced cortisol levels, and context dependence of cortisol modulation in a mammalian species.
Measuring stress in wildlife: techniques for quantifying glucocorticoids
Oecologia, 2011
Stress responses play a key role in allowing animals to cope with change and challenge in the face of both environmental certainty and uncertainty. Measurement of glucocorticoid levels, key elements in the neuroendocrine stress axis, can give insight into an animal's well-being and can aid understanding ecological and evolutionary processes as well as conservation and management issues. We give an overview of the four main biological samples that have been utilized [blood, saliva, excreta (feces and urine), and integumentary structures (hair and feathers)], their advantages and disadvantages for use with wildlife, and some of the background and pitfalls that users must consider in interpreting their results. The matrix of choice will depend on the nature of the study and of the species, on whether one is examining the impact of acute versus chronic stressors, and on the degree of invasiveness that is possible or desirable. In some cases, more than one matrix can be measured to achieve the same ends. All require a significant degree of expertise, sometimes in obtaining the sample and always in extracting and analyzing the glucocorticoid or its metabolites. Glucocorticoid measurement is proving to be a powerful integrator of environmental stressors and of an animal's condition.
Non-invasive cortisol profile: A tool for reproductive stress in female tigers
The Pharma Innovation
Stress can be defined as any internal or external factor that affects the homeostasis of the animal. The factors by which it is caused are called as stressors. Stress is one of the known factors to have an impact on the reproductive physiology of the animals in terms of reduced fertility and sexual behaviour, as, it is believed that the stress hormones have inhibiting effect on gonadotropin releasing hormone. The wild felids are thought to get easily stressed while capturing, which, can have effect on the normal hormonal profile. Non-invasive collection of samples includes the collection of faeces and urine from the animals' enclosure or night cell in captivity without disturbing the normal routine of the animal. Faecal and urine samples of nine adult healthy animals which was deposited in the morning or 24 hours were collected on weekly intervals for 14 weeks from the night cell. Faecal samples were dried and extracted for cortisol by ethanol, whereas, urine puddles were collected from the floor by aspirating with the sterilized syringe. the least average value for faecal and urine cortisol has been found in the third week (4269 ± 932 pg/g) and tenth week (5541 ± 763 pg/mL), whereas, highest mean value for faecal and urine cortisol was observed on the second week (8652 ± 2484 pg/g) and fifth week (42077 ± 31906 pg/mL) respectively. It has shown a significant change between the groups on the first week of the trial for faecal cortisol, in which the lowest average value was exhibited by the G III (2444 ± 1309 pg/g) and the highest in G II (10310 ± 2542 pg/g). However, urine cortisol has shown a significant change between the groups on the fourth week of the trial with the highest value being exhibited by the G III (25250 ± 1380 pg/mL) and lowest in the G I (5183 ± 691 pg/mL). It was observed that the concentration of cortisol remains elevated in unmated group of animals as compared to mated animals.
Canadian Journal of Zoology, 2000
We examined the effect of exposure to a potential predator on cortisol concentrations in captive female Columbian ground squirrels (Spermophilus columbianus) and determined if lactation mitigated this cortisol response. Lactating and nonlactating females were exposed to a dog (Canis familiaris) for 5 min once a week over a 8-week period. Blood was collected 5 min and 2.5 and 4.5 h after exposure to the dog. Females exposed to the dog had higher concentrations of total (but not free) cortisol than unexposed females only in the 5-min blood sample. Over the active season, total-and free-cortisol levels were 37-47% higher in females exposed to the dog than in unexposed females in early to mid-July when young were being weaned. The cortisol response to the dog was suppressed during lactation. Cortisol levels were, on average, 41-59% lower during lactation than during nonlactation 5 min (but not 2.5 or 4.5 h) after exposure to the dog. Résumé : Nous avons évalué les effets de l'exposition à un prédateur en puissance sur les concentrations de cortisol chez des femelles en captivité du Spermophile du Columbia (Spermophilus columbianus) et avons tenté de déterminer si l'allaitement tempère la réaction du cortisol. Des femelles nourricières et des femelles non nourricières ont été mises en présence d'un chien (Canis familiaris) pendant 5 min une fois par semaine pendant 8 semaines. Des prélèvements de sang ont été recueillis sur les spermophiles 5 min, 2,5 h et 4,5 h après l'exposition. Les femelles mises en présence du chien avaient des concentrations de cortisol total (pas le cortisol libre) plus élevées que les femelles témoins seulement dans l'échantillon de sang prélevé 5 min après le traitement. Au cours de la saison active, les concentrations de cortisol total et de cortisol libre étaient 37-47 % plus élevées chez les femelles mises en présence du chien que chez les femelles témoins entre le début et le milieu de juillet pendant la période du sevrage. Pendant l'allaitement la concentration de cortisol des femelles nourricières exposées au chien ne variait pas. Cinq min (mais pas 2,5 ou 4,5 h) après exposition au chien, les concentrations de cortisol étaient en moyenne de 41-59 % plus faibles durant l'allaitement qu'en dehors de la période d'allaitement. [Traduit par la Rédaction] Hubbs et al. 587
Conservation Physiology, 2014
The measurement of cortisol in hair is becoming important in studying the role of stress in the life history, health and ecology of wild mammals. The hair cortisol concentration (HCC) is generally believed to be a reliable indicator of long-term stress that can reflect frequent or prolonged activation of the hypothalamic-pituitary-adrenal axis over weeks to months through passive diffusion from the blood supply to the follicular cells that produce the hair. Diffusion of cortisol from tissues surrounding the follicle and glandular secretions (sebum and sweat) that coat the growing hair may also affect the HCC, but the extent of these effects is thought to be minimal. In this study, we report on a range of factors that are associated with, and possibly influence, cortisol concentrations in the hair of free-ranging brown bears (Ursus arctos). Through two levels of analyses that differed in sample sizes and availability of predictor variables, we identified the presence or absence of capture, restraint and handling, as well as different methods of capture, as significant factors that appeared to influence HCC in a time frame that was too short (minutes to hours) to be explained by passive diffusion from the blood supply alone. Furthermore, our results suggest that HCC was altered after hair growth had ceased and blood supply to the hair follicle was terminated. However, we also confirmed that HCC was inversely associated with brown bear body condition and was, therefore, responsive to diminished food availability/quality and possibly other long-term stressors that affect body condition. Collectively, our findings emphasize the importance of further elucidating the mechanisms of cortisol accumulation in hair and the influence of long-and short-term stressors on these mechanisms.
Assessing stress in animal populations: Do fecal and plasma glucocorticoids tell the same story?
General and Comparative Endocrinology, 2010
Many studies have recently focused on stress as a marker of an animal's well being. Since animals respond to a stressor by increasing their glucocorticoid (GC) levels there has been much interest in measuring these hormones. Fecal GC analyses have been used in a wide range of studies as they are an easily obtained, non-invasive measure of these stress hormones. However, these analyses rest on two major assumptions. First, they assume that fecal GC metabolites reflect free, biologically active levels of GCs in the plasma. Second, they assume that differences in fecal GC metabolite levels among animals are an accurate reflection of their physiological state and thus of their ability to respond to a stressor. We tested these assumptions in a population of free-ranging snowshoe hares (Lepus americanus) in the southwestern Yukon, from 2006 to 2008. Both assumptions were verified. Plasma free cortisol levels mirrored bile and fecal cortisol metabolite (FCM) levels, but plasma total cortisol levels did not. Differences in FCM concentrations among hares robustly predicted their response to a hormonal challenge. Hares with higher FCM concentrations showed a greater resistance to the suppression of their free plasma cortisol following a dexamethasone injection and a more marked increase of free plasma cortisol following an ACTH injection. Furthermore, we found that changes in FCM concentrations in autumn and winter over two years reliably tracked changes in plasma free cortisol levels obtained from the hormonal challenge test. These results indicate that both fecal and plasma measures of an animal's stress physiology are concordant: they tell the same story.
Hormones and behavior, 2014
A fundamental element of how vertebrates respond to stressors is by rapidly elevating circulating glucocorticoid hormones. Individual variation in the magnitude of the glucocorticoid stress response has been linked with reproductive success and survival. But while the adaptive value of this response is believed to stem in part from changes in the expression of hormone-mediated behaviors, it is not clear how the behavior of stronger and weaker glucocorticoid responders differs during reproduction, or during exposure to ecologically relevant stressors. Here we report that in a population of barn swallows (Hirundo rustica erythrogaster) experiencing high rates of nest predation, circulating levels of corticosterone (the primary avian glucocorticoid) during exposure to a standardized stressor predict aspects of subsequent behavior and fitness. Individuals that mounted a stronger corticosterone stress response during the early reproductive period did not differ in clutch size, but fledge...