VALIDATION OF A METHOD FOR MEASURING THE FECAL GLUCOCORTICOID METABOLITES IN THE MIDDAY GERBIL (<i>MERIONES MERIDIANUS</i> PALLAS 1773, MURIDAE, RODENTIA): BIOLOGICAL AND PHYSIOLOGICAL APPROACHES

Abstract

Estimating the level of stress in natural populations opens the opportunities for studying various populational processes, including population dynamics, range expansions, and colonization. Over two last decades, methods for a non-invasive assay of the glucocorticoid levels have been actively developed and widely implemented in various biological fields. They are most suitable for assessing long-term stress, but require a validation procedure for each new animal species studied. We have conducted a biological and physiological validation of a non-invasive method for the determination of fecal glucocorticoid metabolites (FGM) in the Midday gerbil, Meriones meridianus. Both methods showed a significant increase in the concentration of FGM after a similar time after manipulations (4–5 h after the stressful procedures or the administration of ACTH), and peak values were twice the baseline. Saline injection (control group) did not cause a significant increase in FGM concentration, this confirming that the non-invasive measuring a smoothed level of FGM is more suitable for assessing a long-term stress, in contrast to the assay of glucocorticoids in the blood. The biological validation was as effective as ACTG-test, which is commonly considered more reliable. Given the low invasiveness of the biological method, this expands the possibilities for its application. This research was supported by the Russian Science Foundation (project number 22-14-00223, https://rscf.ru/project/22-14-00223/).