Validation of Enzyme Immunoassays via an Adrenocorticotrophic Stimulation Test for the Non-Invasive Quantification of Stress-Related Hormone Metabolites in Naked Mole-Rats

Abstract

Small size in mammals usually restricts long-term, frequent monitoring of endocrine function using plasma as a matrix. Thus, the non-invasive monitoring of hormone metabolite concentrations in excreta may provide an invaluable approach. The aim of the current study was to examine the suitability of enzyme immunoassays (EIAs) for monitoring responses to stressors in the naked mole-rat (Heterocephalus glaber, NMR) using urine and feces as hormone matrices. A saline control administration, and a high- and low-dose adrenocorticotropic hormone (ACTH) challenge were performed on six male and six female disperser morph NMRs. The results revealed that a 5α-pregnane-3β,11β,21-triol-20-one EIA detecting glucocorticoid metabolites (GCMs) with a 5α-3β-11β-diol structure is the most suitable assay for measuring concentrations in male urine samples, whereas an 11-oxoaetiocholanolone EIA detecting GCMs with a 5β-3α-ol-11-one structure appears the most suitable EIA for quantifying GCMs in female urine. An 11-oxoaetiocholanolone EIA detecting 11,17 dioxoandrostanes was the most suitable EIA for quantifying GCMs in the feces of both sexes. There were sex-related differences in response to the high- and low-dose ACTH challenge. We recommend using feces as a more suitable matrix for non-invasive GCM monitoring for NMRs which can be valuable when investigating housing conditions and other welfare aspects.

The dissection of a despotic society: exploration, dominance and hormonal traits

“…By analysing the hormonal status in relation to dominance position our results suggest a finding which may have been overlooked when comparing queens with subordinates as a cohort of non-breeding animals. However, Majelantle et al [47] showed that females showed no increase in fGCM concentrations after low-dose adrenocorticotrophic (ACTH) administration, but had an increase in fGCM after high-dose ACTH administration suggesting that females only respond to more distinct stressful events. Thus, the high-ranking females are probably subjected to targeted high stressors from the queen in the form of shoving events [44].…”

“…It is unlikely that the difference in the order of procedure affected the overall behaviour and stress-related endocrine correlates of naked mole-rats in our study. For example, after adrenocorticotrophic hormone and saline administration to the species, stress-related hormones for males returned to baseline 96 h post-administration, and females showed decreases in stress-related hormones 120 h post-administration [47].…”

“…Faecal glucocorticoid metabolite (fGCM), faecal androgen metabolite (fAM) and faecal progestagen metabolite (fPM) concentrations were measured using a 11-oxoaetiocholanolone enzyme immunoassay (EIA) [54], an epiandrosterone EIA [55] and 5α-tetrahydroprogesterone EIA [56], respectively. These EIAs were previously identified as suitable for quantifying fGCMs [47], fAMs and fPMs [57] in naked mole-rats. Quantifications were conducted following Ganswindt et al [58].…”