Pathogenetic characteristics of the hormonal profile in rats subjected to restraint stress of different duration

Abstract

The aim of the work is to ascertain the character of changes in the hormonal profile (concentrations of corticosterone, insulin, and adrenocorticotropic hormone) in conjunction with metabolic alterations and elevated blood pressure, which are induced in rats by restraint stress at 6th, 15th and 21st weeks of environmental space restriction. Materials and methods. A total of 55 normotensive male Wistar rats, aged 6–10 months, were assigned into 4 experimental groups (1 – intact control (10 rats); 2, 3 and 4 (15 rats each exposed to restricted space allowance)). All the animals were subjected to blood pressure (BP), blood glucose level and body weight measurements twice: at the stage of forming groups and at the 6th, 15th and 21st weeks. Plasma hormone concentrations (insulin, corticosterone, and ACTH) were examined by the immunoenzymatic method using commercial kits (Monobind, USA). Results. The body weight of the animals was significantly reduced by 20.72 % after 6 weeks of space allowance restriction, it was restored to baselines by the 15th week and exceeded control values by 26.1 % at the 21st week. BP levels showed an increasing trend, a dynamic increase in systolic pressure by 7 %, 17 % and 26 % was detected, respectively, as well as diastolic from the 15th week to the 21st week by 21.4 % and 37.0 %, respectively. Glucose concentration was within the euglycemic range. Changes in the hormonal profile showed an increase in the concentration of ACTH by more than 50 % and a decrease in insulin – by 34 % at the 6th week with a subsequent twofold decrease in the insulin concentration (at week 15) and a further more than twofold increase in ACTH at the 21st week. As for changes in the concentration of corticosterone, a peak increase of 3.77 times was noticed at the 15th week, followed by a decrease and restoration to the normative values by the 21st week. Conclusions. Even minor and unremarkable continuously acting stressors, which cannot be coped, become important triggers for hormonal profile and carbohydrate metabolism alterations as well as for a persistent increase in blood pressure, which manifest first by hypoinsulinemia, an increase in the level of ACTH, and a constant concentration of corticosterone. Long-term stress exposure contributes to a transient “peak” increase in the corticosterone level, a significant increase in insulin and a sustained increase in ACTH. Multidirectional changes in the levels of the studied hormones occur amidst a gradual increase in blood pressure and a stable increase in the level of glycemia.

Keywords

• insulin
• corticosterone
• adrenocorticotropic hormone
• blood pressure
• stress
• rats