Laparotomy Causes a Transient Induction of Rat Liver Serine Dehydratase mRNA

Rat liver serine dehydratase mRNA shows rhythmicity with a high level at the onset of dark (19:00) and a low level at the onset of light (07:00). We have examined the effect of stress (laparotomy) on the rhythm, Upon laparotomy at 09:00 or 17:00, a marked induction of serine dehydratase mRNA occurred 2 h after operation. The elevated mRNA level then decreased and the original mRNA rhythm resumed 2 days later. By contrast, the transcription activator protein DBP mRNA level which shows a similar oscillation was not affected by this treatment. The induction was also seen in adrenalectomized rats that had been treated with hydrocortisone but not with saline or noradrenaline, indicating that glucocorticoids are absolutely necessary for the induction. Pretreatment of rats with phenoxybenzamine, and prazosin prevented the effect of laparotomy, but propranolol and yohimbine had no effect, indicating the necessity of the α1-adrenergic stimulation for the induction. These results suggest that laparotomy releases glucocorticoids and neural noradrenaline that stimulates α1-adrenergic receptors, thereby leading to the serine dehydratase gene expression.