Glucocorticoid receptor mRNA expression in peripheral blood mononuclear cells in high trained compared to low trained athletes and untrained subjects.
BACKGROUND
Physiological needs during prolonged exercise are a potent stimulus for the hypothalamic-pituitary-adrenal (HPA) axis. Hence, athletes undergoing daily endurance training sessions may have frequent and prolonged phases of endogenous hypercortisolism. Since chronic glucocorticoids treatment leads to down-regulation of glucocorticoid receptor alpha (GR-alpha) mRNA expression, endurance training could lead to modulation of GR expression.


OBJECTIVE
The aim of the study was to evaluate GR-alpha and GR-beta mRNA expressions in peripheral blood mononuclear cells and plasma cortisol, ACTH and cortisol binding globulin (CBG) concentrations at rest in subjects undergoing different training regimes.


METHODS
Nine high trained (HT) swimmers (training volume: 21.6+/-1.7 hours/week in 10-12 sessions) were compared with two age-matched control groups represented by 8 low trained (LT) runners (training volume: 6.4+/-2.6 h/week in 3-5 sessions) and 9 untrained subjects. Expression of GR was determined by RT-PCR of total RNA. Hormone levels were determined by radioimmunoassay methods.


RESULTS
HT athletes showed 10 times less GR-alpha mRNA expression than the untrained subjects, while LT athletes exhibited values about twofold less than the untrained subjects. GR-beta mRNA expression was undetectable in all subjects. No differences were observed among the three groups in hormone levels.


CONCLUSIONS
GR- alpha mRNA expression is repressed in proportion to the amount and frequency of the stressful stimuli due to training. Hence, this down-regulation may be a consequence of the frequent and prolonged exposure to cortisol acute elevations induced by training. GR-beta did not play an important role in inducing the down-regulation of GR-alpha mRNA expression observed.
Bonifazi
M
M
Department of Physiology, University of Siena, Via Aldo Moro, I-53100 Siena, Italy. bonifazi@unisi.it
Mencarelli
M
M
Fedele
V
V
Ceccarelli
I
I
Pecorelli
A
A
Grasso
G
G
Aloisi
A M
AM
Muscettola
M
M
D000324:Adrenocorticotropic Hormone / Q000097:blood; D000328:Adult; D000704:Analysis of Variance; D056352:Athletes; D002352:Carrier Proteins / Q000097:blood; D002478:Cells, Cultured; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D015592:Immunoradiometric Assay; D007963:Leukocytes, Mononuclear / Q000378:metabolism*; D008297:Male; D010807:Physical Endurance / Q000502:physiology*; D010809:Physical Fitness / Q000502:physiology*; D020033:Protein Isoforms / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011863:Radioimmunoassay; D011965:Receptors, Glucocorticoid / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012420:Running / Q000502:physiology; D011795:Surveys and Questionnaires; D013550:Swimming / Q000502:physiology
D002352:Carrier Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid; C027091:cortisol binding globulin; D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone