Comparison of different enzymeimmunoassays for assessment of adrenocortical activity in primates based on fecal analysis

Abstract

Most studies published to date that used fecal glucocorticoid measurements to assess adrenocortical activity in primate (and many nonprimate) species applied a specific cortisol or corticosterone assay. However, since these native glucocorticoids are virtually absent in the feces of most vertebrates, including primates, the validity of this approach has recently been questioned. Therefore, the overall aim of the present study was to assess the validity of four enzyme-immunoassays (EIAs) using antibodies raised against cortisol, corticosterone, and reduced cortisol metabolites (two group-specific antibodies) for assessing adrenocortical activity using fecal glucocorticoid metabolite (GCM) measurements in selected primate species (marmoset, long-tailed macaque, Barbary macaque, chimpanzee, and gorilla). Using physiological stimulation of the hypothalamo-pituitary-adrenocortical (HPA) axis by administering exogenous ACTH or anesthesia, we demonstrated that at least two assays detected the predicted increase in fecal GCM levels in response to treatment in each species. However, the magnitude of response varied between assays and species, and no one assay was applicable to all species. While the corticosterone assay generally was of only limited suitability for assessing glucocorticoid output, the specific cortisol assay was valuable for those species that (according to high-performance liquid chromatography (HPLC) analysis data) excreted clearly detectable amounts of authentic cortisol into the feces. In contrast, in species in which cortisol was virtually absent in the feces, group-specific assays provided a much stronger signal, and these assays also performed well in the other primate species tested (except the marmoset). Collectively, the data suggest that the reliability of a given fecal glucocorticoid assay in reflecting activity of the HPA axis in primates clearly depends on the species in question. Although to date there is no single assay system that can be used successfully across species, our data suggest that group-specific assays have a high potential for cross-species application. Nevertheless, regardless of which GC antibody is chosen, our study clearly reinforces the necessity of appropriately validating the respective assay system before it is used.

Responses to social and environmental stress are attenuated by strong male bonds in wild macaques

“…This aggression rate value was then matched to the average fGCM value obtained from the one to three fecal samples collected in the corresponding 10-d period (allowing for a 2-d lag in hormone excretion). We used 2 d because changes in blood hormone levels can be detected in fecal hormone metabolite levels after about 24-56 h in macaques in radiometabolism studies and experimentally induced HPA axis activation experiments (87,91). We then constructed an LMM (58) to examine the effect of the social factors on fGCM levels.…”

The hustle and bustle of city life: monitoring the effects of urbanisation in the African lesser bushbaby

“…Monitoring stress responses non-invasively has allowed scientists to gain unique insights into the response to stressors, even for species that are difficult to assess in the wild (Heistermann et al 2006;Touma and Palme 2005). However, assays for non-invasive hormone measurements need to be carefully validated in terms of applicability for the species-specific hormone matrix of interest to ensure a reliable quantification of respective glucocorticoid metabolites (Touma and Palme 2005).…”

Species-specific patterns in fecal glucocorticoid and androgen levels in zoo-living orangutans (Pongo spp.)

“…A native cortisol assay (described by Palme and Möstl [50]) and two cortisol metabolite assays (11b-hydroxyetiocholanolone, described by [16], and 11-oxoetiocholanolone, described by Möstl et al [42]), were tested for their reliability in reflecting adrenocortical activity from orangutan fecal samples. All three assays have already been successfully used to monitor GC output in various other primate species [15,47], including great apes [23]. Specifically, fecal samples (n = 69, not listed in Table 1) were collected from two adult females before and after transport as part of their relocation to another zoo.…”