Stress and adaptation to repeated stress changed the expression of two isoforms of 11β-hydroxysteroid dehydrogenase (11β-HSD1 and 11β-HSD2) in the adrenal glands of sheep

Abstract

The aim of this study was to estimate rate of cortisol release from ewe’s adrenal gland cortex and medulla tissue and the participation 11β-HSD1 and 2 in modulating adrenal glucocorticosteroids release, determine the expression size of these two isoforms in both parts of adrenal glands after single and repeated stress (3 times every 24h), when adaptive processes take place. The experiment was carried on 15 ewes, outside the breeding season. The research material consisted of adrenal glands obtained from control sheep (CON), sheep subjected to one-hour individual isolation from the herd (S1) and three times repeated stress factor at one-day intervals (S2). Immediately after slaughter, the adrenal glands from each sheep were placed on ice in 0.9% NaCl, then they were cut into smaller sections of similar weight (approx. 50 mg), covering the cortical and medullary layers of the adrenal glands. Sections of obtained tissues were weighed and placed in incubation wells (Sigma cell culture) containing 1 ml of incubation Eagle's medium with the addition of bovine albumin (BSA, 50 mg / 100 ml). Tissue incubation was carried out in an atmosphere of carbogen - 95% O2 and 5% CO2 at 38oC in a Sanyo incubator (MCO-18AIC). After 10 minutes of stabilization, the sections of core and adrenal cortex tissue were transferred to subsequent wells containing pure Eagle Medium. The same section was transferred to consecutive incubation wells containing clean incubation medium every 30 minutes. The medium harvested from the wells after 30, 60 and 90 minutes of incubation of adrenal tissue was frozen until the scheduled cortisol concentration de-termination by RIA (Orion Diagnostica) was performed. Another pieces of tissue the cortex and adrenal medulla from each sheep immediately placed in the RNAlater. Measurements of the gene expression of 11β-HSD1 and 2 expression in the adrenal cortex and medulla were performed using Real-time qPCR method. Starters and TaqMan MGB probes were designed by Applied Biosystem. In the conducted in vitro experiment, a significant reduction in the amount of cortisol released from adrenal cortex tissue into the medium after single stress factor was found, from 3.27 ± 0.69 pg･mg-1 tissue after first 30 minutes of experiment to 0.70 ± 0.15 pg･mg-1 of tissue after 90 minutes (P < 0.01). A similar profile of cortisol release from the adrenal cortex tissue was found in control sheep (P > 0.05). Experimental Group 2 (S2) had a similar profile of cortisol release during the all-time of incubation, however the values found were always lower than those observed in the control and single stress sheep Experimental Group 1 (S1) (1.34 ± 0.37 to 0.30 ± 0.08 pg･mg-1 of tissue; P < 0.05). After repeated stress, incubation of adrenal cortex tissue showed a similar profile of changes in cortisol release, however the values were significantly lower than those found in the singly stressed animals (from 1.30 ± 0.37 pg･mg-1 after 30 minutes to 0.27 ± 0.08 pg･mg-1 tissue after 90 minutes; P < 0.01). Incubation of adrenal medulla tissue obtained from singly stressed animals showed cortisol release to the medium much lower in comparison to adrenal cortex layer, however constant during the whole incubation time, value 1.04 ± 0.36 pg/mg-1 tissue noted after first 30 minutes to 0.77 ± 0.06 pg･mg-1 after 90 minutes of experiment; P > 0.05). When the stress factor was repeated three times, the amount of cortisol released was like that observed in the control secretion; P > 0.05). Analysis of 11β-HSD 1 expression in adrenal cortex tissue from singly stressed sheep showed an over threefold increase (350 ± 25 RQ), while measurement after stress factor was repeated three times demonstrated increase, however the value turned out to be two times lower than after a single stress (160 ± 35 RQ). The expression value of 11β-HSD 2 in the adrenal cortex tissue showed a significant reduction after both single (15 ± 7 RQ and repeated stress (22 ± 3.0 RQ). No significant differences were found in the expression value of this enzyme in the sheep adrenal medulla in both experimental groups in comparison to control group (P > 0.05). The obtained results indicate the immanent abilities of the adrenal glands, probably to a certain extent, to control the release of cortisol, conditioned by the presence and variable activity of the enzyme 11β-HSD, particularly isoform 1, in adrenal glands without the need to activate all HPA axis structures during stress and adaptation processes.