Transient or sustained transcriptional activation of the genes encoding rat adrenomedullary catecholamine biosynthetic enzymes by different durationsof immobilization stress

The impact of stress on the transcription of rat adrenal tyrosine hydroxyla se and dopamine beta-hydroxylase genes was examined. Nuclear run-on assays revealed that repeated immobilization stress elicited marked (about threefo ld) increases in the relative rates of transcription, being sustained for a t least one day. Parallel changes in the steady-state messenger RNA levels for tyrosine hydroxylase and dopamine beta-hydroxylase were also observed. A single episode of stress triggered similar enhancements in their relative transcription rates. Depending on the duration of the stress signal, the e ffect on gene transcription varied in its persistence. After very short (5 min) immobilization, there was a marked transient rise in the transcription of both genes, without an accumulation of the corresponding mRNAs. Longer episodes of stress (30 min) increased the relative rate of tyrosine hydroxy lase transcription for hours, causing elevations in the steady-state messen ger RNA levels. In contrast, although dopamine beta-hydroxylase transcripti on was elevated to a similar extent by 30-min immobilization stress, the ef fect was transient and not reflected in significant accumulation of its mes senger RNA. The results of our studies emphasize that the stress-evoked increases in th e expression of the genes encoding adrenomedullary catecholamine biosynthet ic enzymes involve transcriptional activation. Depending on the duration an d reiteration of the stress signal, different transcriptional mechanisms ma y be employed. (C) 1999 IBRO. Published by Elsevier Science Ltd.