OBJECTIVE: Isolation of adult animals represents a form of psychsocial stress that produces sympatho-adrenomedullar activation. The aim of this work was to investigate the changes in gene expression and protein levels of catecholamine biosynthetic enzymes: tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH) and phenylethanolamine N-methyltransferase (PNMT) in the adrenal medulla of naive control and chronically (12 weeks) socially isolated adult Wistar rat males and the response of these animals to additional immobilization stress (2 h).
METHODS: TH, DBH and PNMT mRNA levels were quantified by quantitative real-time RT-PCR (qRT-PCR). TH, DBH and PNMT immunoproteins were assayed by Western Blot.
RESULTS: In chronically isolated rats, gene expression levels of catecholamine biosynthetic enzymes in the adrenal medulla were decreased, but only TH mRNA was significantly decreased. However, protein levels of TH, DBH and PNMT of these animals were elevated by 55%, 20% and 18%, respectively, in relation to the corresponding control. Naive control and chronically socially isolated rats exposed to additional 2-h-immobilization showed increased gene expression of the examined enzymes, the increase being greater in socially isolated rats as compared to the controls. Additional immobilization of naive controls did not affect TH, DBH and PNMT protein levels. In contrast, this stress produced increased TH, DBH and PNMT protein levels in long-term socially isolated rats.
CONCLUSION: We can conclude that psychosocial stress expressed a differential influence on gene expression and protein levels of catecholamine biosynthetic enzymes in the adrenal medulla of adult rats. The results indicate a possible adaptation of catecholamine-synthesizing system at the level of TH gene expression in adrenal medulla of chronically isolated animals.