INFLUENCE OF CHRONIC STRESS ON HEMODYNAMIC INDICES, DIURNAL FLUCTUATION OF CATECHOLAMINES PLASMA CONCETRATIONS AND REMODELLING OF VARIOUS ORGANS IN RATS

Abstract

Stress condition combines the different type of emotional, physical and psychological alterations in response to various stressor. Stress may result in favourable outcome by leading to a new biological balance or sometimes can exert damaging dangerous effect including changes in function of cardiovascular system. For this reason, individual approach to stress accompanied cardiovascular somatovegetative correlates alterations is one of the important directions in modern cardiology.

The goal of the present study was the investigation of cardiohemodynamic parameters, catecholamines plasma level alterations and remodelling of different organs in chronic immobilization stress and its coincident with isolation stress.

Experiments were performed on 75 male Wistar rats weighing 200-250g divided into three groups: I- Stress naive animals control (C) group; II – rats exposed to chronic immobilization stress (CIZS) and CIZS animals with coincident chronic isolation stress (CISS). Rats were handled in compliance with ethical standards approved by the Animal Care Committee of Tbilisi State Medical University. CIZS was created by placing rats in a special plexiglas transparant camera for 120 min every day in the morning (10⁰⁰-12⁰⁰) hours during 21 days, with retained their ability to turn a head with restriction body and paws movement. Each rat from III group after submitted to CIZS vs II groip of animals was maintained in cage separately. Cardiovasular parameters including systolic (S), diastolic (D) blood pressure (BP) and heart rhythm (HR) were obtained by non-invasive „tail-cuff“ sphygmomanometric method. Catecholamines norepinephrine (NE) and epinephrine (EPN) blood level daily fluctuation was studied at 5 different points (9:00, 13:00, 17:00, 21:00, 01:00 h) to determine the acrophases in this period. Stress influence on body weight and remodeling of various organs was studied by changes of their masscs.

It was established the CIZS induced significant changes in hemodynamic indices with gradual elevation in SBP, DBP and HR after 14 days to stress exposure, attaining peak values after 21 days to stress submission - 138±4 mmHg (P<0,01), 99±4 mm Hg (P<0,05) and 472±6 beat/min (P<0,01), respectively vs. the same values in C rats: 106±8 mm Hg, 72±7 mm Hg and 414±6 beat/min, respectively. In CIZS +CISS exposed rats revealed more pronounced changes with respect to C and CIZS group of animals indicated about marked influence of heterotypic stress intervention to homotypic ones. Cardiovascular alterations in CIZS animals were associated with significant increased mean plasma levels of NE-456,5±28,6 pg/ml and EPN-563±25,2, respectively vs. C rats with shifted their acrophases from light hours (19⁰⁰-17⁰⁰h) revealed in C rats to evening and late-night hours (17⁰⁰-01⁰⁰h) in stress exposed animals. Catecholamines plasma level elevation in combine stress condition outnumbered the same values in CIZS exposed rats. Along with abovementioned, both type of stress characterized with decreased: body weight, kidney and lymphoid organs (spleen, thymus) masses and increased in adrenals and thyroid organs weights.

It is postulated that prolong chronic homotypic stress characterized with significant alterations of cardiovascular indices expressed in increased BP and HR, associated with elevation in catecholamines plasma level and shifting their acrophases from light to evening and late-night hours. Such alterations are more revealed in combine stress condition without habituation concerning such changes.