Abstract
Cortisol measurements of hair are becoming a valuable tool in monitoring chronic stress. To further validate this approach in domestic dogs, we compared the variability of cortisol immunoreactivity in hair with that in saliva and feces of dogs housed under constant social and physical conditions. Fecal (n = 268), and hair (n = 21) samples were collected over 3 mo from 7 dogs housed in a kennel and kept for training veterinary students in minimally invasive procedures. Salivary samples (n = 181) were collected 3 times daily twice weekly during the last month of the study. Hair and salivary samples were analyzed by enzyme immunoassay and feces by radioimmunoassay. HPLC coupled with tandem mass spectrometry was used to confirm the presence of cortisol in 3 hair samples. Variability of cortisol was compared across sample types by using repeated-measures ANOVA followed by paired t tests. Within dogs, cortisol immunoreactivity was less variable in hair than in saliva or feces. Averaged over time, the variability of fecal samples approached that of hair when feces were collected at least 4 times monthly. As predicted, the stable social and environmental condition of the dogs maintained repeatability over time and supported the hypothesis that data from hair samples reflect baseline cortisol levels. These findings indicate that determining cortisol immunoreactivity in hair is a more practical approach than is using samples of saliva or feces in monitoring the effects of long-term stressors such as social or physical environments and disease progression.
Glucocorticoids are well-established biomarkers of stress in vertebrates, including birds,6 fish, and mammals. Stress—though adaptive in the short term—has been linked with impaired health and ultimately decreased fitness over prolonged periods. Consequently, measuring cortisol or other glucocorticoids over time can reveal how animals respond to prolonged stressors such as changes in their social or physical environments.
Hair is now recognized as a valuable matrix for measuring cortisol in humans and other mammals. In contrast to biologic samples that reflect circulating steroid levels integrated over seconds to hours (for example, serum, saliva, urine, feces), hair integrates steroids over the entire period of hair growth (months to years).Additional advantages are that hair can be collected relatively noninvasively, is easy to store even for long periods, and is not affected by the short-term stress of handling. In a research setting, hair could be shaved at regular intervals to monitor chronic stress. Alternatively, hair could potentially be segmented to provide a retrospective record of cortisol concentrations;this approach would be valuable for documenting the progression of endocrine diseases such as Cushing syndrome in domestic animals presenting with symptoms for the first time and in studying wild animals that can be captured only once.
The currently accepted mechanism for steroid incorporation into growing hair is via the blood vessel that feeds the follicle and potentially from surrounding eccrine and sebaceous glands. Another possibility is that the follicle itself produces cortisol locally in coordination with a broader systemic stress response, in response to localized skin irritation or as part of normal hair follicle functioning. Once inside the follicle, binding of cortisol to the hair fiber is complex and likely involves both melanins and keratin. Regardless of the mechanism, cortisol concentrations in hair have been shown to reflect well-known endocrine patterns. One study in macaques showed a correlation between cortisol levels in hair and saliva. Two other studies have examined the relationship in dogs: one compared cortisol levels in hair and feces and the other compared cortisol data from hair and saliva. In both of these studies hair was collected only once from a single dog and compared with only one other tissue.
The primary objective of the current study was to build on these previous findings by evaluating the variability of hair-based measures of cortisol in a population of dogs with a common environment and diet. We hypothesized that cortisol immunoreactivity in hair would be less variable than that in saliva and feces. In addition, we designed the experiment to allow comparison of data from hair with that of both feces and saliva. We predicted that cortisol immunoreactivity in hair would correlate positively with that in saliva and feces averaged over a corresponding time period. Finally, we used HPLC coupled with tandem mass spectrometry (LC-MS/MS) as a ‘gold standard’ for confirming the presence of cortisol in dog hair.
Resource: http://www.ncbi.nlm.nih.gov
Cortisol measurements of hair are becoming a valuable tool in monitoring chronic stress. To further validate this approach in domestic dogs, we compared the variability of cortisol immunoreactivity in hair with that in saliva and feces of dogs housed under constant social and physical conditions. Fecal (n = 268), and hair (n = 21) samples were collected over 3 mo from 7 dogs housed in a kennel and kept for training veterinary students in minimally invasive procedures. Salivary samples (n = 181) were collected 3 times daily twice weekly during the last month of the study. Hair and salivary samples were analyzed by enzyme immunoassay and feces by radioimmunoassay. HPLC coupled with tandem mass spectrometry was used to confirm the presence of cortisol in 3 hair samples. Variability of cortisol was compared across sample types by using repeated-measures ANOVA followed by paired t tests. Within dogs, cortisol immunoreactivity was less variable in hair than in saliva or feces. Averaged over time, the variability of fecal samples approached that of hair when feces were collected at least 4 times monthly. As predicted, the stable social and environmental condition of the dogs maintained repeatability over time and supported the hypothesis that data from hair samples reflect baseline cortisol levels. These findings indicate that determining cortisol immunoreactivity in hair is a more practical approach than is using samples of saliva or feces in monitoring the effects of long-term stressors such as social or physical environments and disease progression.
Glucocorticoids are well-established biomarkers of stress in vertebrates, including birds,6 fish, and mammals. Stress—though adaptive in the short term—has been linked with impaired health and ultimately decreased fitness over prolonged periods. Consequently, measuring cortisol or other glucocorticoids over time can reveal how animals respond to prolonged stressors such as changes in their social or physical environments.
Hair is now recognized as a valuable matrix for measuring cortisol in humans and other mammals. In contrast to biologic samples that reflect circulating steroid levels integrated over seconds to hours (for example, serum, saliva, urine, feces), hair integrates steroids over the entire period of hair growth (months to years).Additional advantages are that hair can be collected relatively noninvasively, is easy to store even for long periods, and is not affected by the short-term stress of handling. In a research setting, hair could be shaved at regular intervals to monitor chronic stress. Alternatively, hair could potentially be segmented to provide a retrospective record of cortisol concentrations;this approach would be valuable for documenting the progression of endocrine diseases such as Cushing syndrome in domestic animals presenting with symptoms for the first time and in studying wild animals that can be captured only once.
The currently accepted mechanism for steroid incorporation into growing hair is via the blood vessel that feeds the follicle and potentially from surrounding eccrine and sebaceous glands. Another possibility is that the follicle itself produces cortisol locally in coordination with a broader systemic stress response, in response to localized skin irritation or as part of normal hair follicle functioning. Once inside the follicle, binding of cortisol to the hair fiber is complex and likely involves both melanins and keratin. Regardless of the mechanism, cortisol concentrations in hair have been shown to reflect well-known endocrine patterns. One study in macaques showed a correlation between cortisol levels in hair and saliva. Two other studies have examined the relationship in dogs: one compared cortisol levels in hair and feces and the other compared cortisol data from hair and saliva. In both of these studies hair was collected only once from a single dog and compared with only one other tissue.
The primary objective of the current study was to build on these previous findings by evaluating the variability of hair-based measures of cortisol in a population of dogs with a common environment and diet. We hypothesized that cortisol immunoreactivity in hair would be less variable than that in saliva and feces. In addition, we designed the experiment to allow comparison of data from hair with that of both feces and saliva. We predicted that cortisol immunoreactivity in hair would correlate positively with that in saliva and feces averaged over a corresponding time period. Finally, we used HPLC coupled with tandem mass spectrometry (LC-MS/MS) as a ‘gold standard’ for confirming the presence of cortisol in dog hair.
Resource: http://www.ncbi.nlm.nih.gov
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