Hair in 'stress': Analyze with care

March 12, 2020

Similar to humans, wild animals' reaction to disturbance is accompanied by releasing hormones, such as cortisol. To understand the impact of various "stress" factors - for example, competition for food, encounters with predators, or changing environmental conditions - on wildlife, scientists first need to determine the baseline levels of relevant hormones for each species. Researchers from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) now uncovered possible pitfalls of the commonly used hormone analysis method that overestimate concentrations of cortisol and thus lead to overstated conclusions. They investigated whether glucocortiocoid hormones deposited in animal hair can be reliable biomarkers to indicate the impact of disturbances. The source of errors in the commonly used antibody-based enzyme immunoassays (EIA) method is described in a recently published article in the scientific journal "Conservation Physiology".

Scientists led by Prof. Katarina Jewgenow, head of the Department of Reproduction Biology at Leibniz-IZW, conducted a comparative analysis on the hair samples from six mammalian species: Egyptian mongoose (Herpestes ichneumon), Iberian lynx (Lynx pardinus), cheetah (Acinonyx jubatus), spotted hyena (Crocuta crocuta), Asiatic black bear (Ursus thibetanus), and Alpine marmot (Marmota marmota). They measured the concentration of the "stress" hormone cortisol in hair extracts using the widely applied method of antibody-based enzyme immunoassays (EIA). This method is based on the ability of an antibody to recognize a three-dimensional molecule structure specific to a particular hormone. Such antibodies will also bind to closely related molecules which express similar structures. Usually such "group"-specific antibodies are very useful for wildlife species - where the relevant "stress" hormone is often unknown - but it also means that the concentration of other substances might be measured that are irrelevant to the biological process under observation, in the case of "stress" hormones such as cortisol to a stressful situation.

To be certain that the natural hormone was extracted from mammalian hair the researchers compared the EIA results to a more comprehensive and precise procedure, a mass spectrometry analysis. They discovered significant discrepancies in the indicated hormone levels. The EIA overestimated the concentration of cortisol by up to ten times. Further biochemical analysis showed that this overestimate was not connected with any substance related to cortisol, but rather to unknown hair born molecules. For that reason they strongly recommend a careful validation of each EIA before using it to the analysis of hormones from hair samples. As it is already known that age, sex and time of the year might influence baseline hair cortisol level, information about age and sex of the individual and the sampling date should also be available.

In a previous study Leibniz-IZW doctoral student Alexandre Azevedo analysed hair samples of Egyptian mongooses (Herpestes ichneumon) from seven provinces of Portugal. He and his colleagues wanted to know whether the successful reintroduction of the Iberian lynx to Portugal is a stressful influence on the mongoose population as the Iberian lynx is a direct food competitor to the mongoose, but lacked a suitable method.

Collecting hair samples is currently frequently suggested as a non-invasive way of assessing "stress" levels as they can be collected without disturbing the animal. "Taking blood samples to measure cortisol concentrations in the serum itself causes considerable stress. Cortisol metabolites can also be detected in faeces, but finding out which individual defecated is quite complicated in free-ranging animals unless the defecation was actually witnessed by the observer", says Jewgenow. "In contrast, hair samples are often obtained in a minimally invasive way using 'hair-traps' which are usually installed to collect samples for genetic analyses from wildlife population." Now such samples can also be used to determine the concentration of cortisol in hair provided the analytical method has been previously validated.
-end-


Forschungsverbund Berlin

Related Stress Articles from Brightsurf:

Stress-free gel
Researchers at The University of Tokyo studied a new mechanism of gelation using colloidal particles.

Early life stress is associated with youth-onset depression for some types of stress but not others
Examining the association between eight different types of early life stress (ELS) and youth-onset depression, a study in JAACAP, published by Elsevier, reports that individuals exposed to ELS were more likely to develop a major depressive disorder (MDD) in childhood or adolescence than individuals who had not been exposed to ELS.

Red light for stress
Researchers from the Institute of Industrial Science at The University of Tokyo have created a biphasic luminescent material that changes color when exposed to mechanical stress.

How do our cells respond to stress?
Molecular biologists reverse-engineer a complex cellular structure that is associated with neurodegenerative diseases such as ALS

How stress remodels the brain
Stress restructures the brain by halting the production of crucial ion channel proteins, according to research in mice recently published in JNeurosci.

Why stress doesn't always cause depression
Rats susceptible to anhedonia, a core symptom of depression, possess more serotonin neurons after being exposed to chronic stress, but the effect can be reversed through amygdala activation, according to new research in JNeurosci.

How plants handle stress
Plants get stressed too. Drought or too much salt disrupt their physiology.

Stress in the powerhouse of the cell
University of Freiburg researchers discover a new principle -- how cells protect themselves from mitochondrial defects.

Measuring stress around cells
Tissues and organs in the human body are shaped through forces generated by cells, that push and pull, to ''sculpt'' biological structures.

Cellular stress at the movies
For the first time, biological imaging experts have used a custom fluorescence microscope and a novel antibody tagging tool to watch living cells undergoing stress.

Read More: Stress News and Stress Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.