NEW APPROACH TO STRESS RESEARCH IN PHOCIDS-POTENTIAL OF DEHYDROEPIANDROSTERONE AND CORTISOL/DEHYDROEPIANDROSTERONE RATIO AS MARKERS FOR STRESS IN HARBOR SEALS ( PHOCA VITULINA) AND GRAY SEALS ( HALICHOERUS GRYPUS).

Cortisol is known to reflect the level of the stress response. However, measuring the cortisol concentration only once fails to provide sufficient information about the duration of the stress exposure. Moreover, handling is an acute stressor and increases cortisol secretion especially in wildlife species. Yet, in phocids reliable indicators are missing that reflect potential chronic effects of stress. The adrenal-derived steroid hormone dehydroepiandrosterone (DHEA) has been described as biomarker for the assessment of the stress status but has not been applied to marine mammal stress research. Therefore, DHEA, the sulfated precursor DHEAS and the cortisol/DHEA ratio were determined in serum of different seals. One group consisted of harbor ( Phoca vitulina) and gray seals ( Halichoerus grypus) that were habituated to human handling. The other two groups included healthy and free-ranging seals suffering from a disease. Blood samples were taken from 11 habituated (six males, five females), 17 wild_healthy (13 males, four females), and nine wild_diseased seals (four males, five females). No differences in serum cortisol levels could be detected between wild_healthy and wild_diseased seals. On the contrary, wild_diseased seals showed the lowest DHEA concentration compared to the other two groups. Wild_diseased seals also revealed the highest cortisol/DHEA ratio compared to the habituated_zoo (2,074.7 ± 351.4 vs. 121.5 ± 26.8, P < 0.001) and wild_healthy seals (827.9 ± 214.3, P < 0.01). DHEA and the cortisol/DHEA ratio may reflect differences in the functionality of the hypothalamic-pituitary-adrenal axis and therefore represent valuable tools for the assessment of stress-related effects in seals.

Dehydroepiandrosterone and cortisol/dehydroepiandrosterone ratios in dairy cattle with postpartum metritis.

Dehydroepiandrosterone (DHEA), a C19 steroid synthesized predominantly by the adrenal cortex, and its sulfated precursor (DHEAS) has antiglucocorticoid and immunoprotective properties. DHEA is important in modulating inflammatory responses; therefore, we hypothesized that DHEA concentrations might be altered in bovine postpartum metritis. DHEA, DHEAS, the cortisol/DHEA-ratio (C/D-ratio) and the DHEAS/DHEA ratio were determined in cows with and without clinical metritis subcategorized by the blood leukocyte numbers. Blood from the coccygeal vein of 37 pluriparous Holstein-Friesian cows was sampled 8.8±0.9days (mean±SE) after calving. Based on clinical signs of metritis and leukocyte numbers (normal range 5-10×106/µl), cows were classified as healthy with leukocyte numbers in the reference range (leukocyte normal; LNH=5954.17±302.4/µl); suffering from metritis with normal leukocyte counts (LNM=7422.22±774.74/µl); or metritis with leukopenia (LLM=3950±284.31/µl P<0.01). Cows with metritis had higher DHEA concentrations than healthy cows (P<0.05). Notably, cows with both metritis and leukopenia displayed higher DHEA concentrations than cows with metritis and normal leukocyte numbers (DHEA LLM 8.15±3.09 vs. LNM 4.09±1.82ng/ml, P<0.05). Cows with metritis and leukopenia also had lower C/D-ratios than healthy cows. In conclusion, DHEA and the cortisol/DHEA-ratio could represent an anti-inflammatory signal during prolonged inflammation of the reproductive tract in dairy cattle and may be a biomarker or prognostic indicator for evaluating disease severity, as seen in serious chronic illnesses in other species.