Noradrenaline concentration and turnover in different regions of the gastrointestinal tract of the rat: an approach to the evaluation of sympathetic activity in the gut.

The endogenous noradrenaline concentration, fractional turnover, half-life, and turnover rate of tritiated ((3)H) noradrenaline were determined in the oesophagus, non-glandular and glandular portions of the stomach, duodenum, jejunum, ileum, and colon of the rat. The highest concentration of endogenous noradrenaline was present in the duodenum and colon. The (3)H-noradrenaline fractional turnover rates and half-lives were significantly greater in the small and large intestines as compared with the oesophagus and stomach. The noradrenaline turnover rate, which is an estimate of the level of sympathetic activity, was greatest in the colon and duodenum. This method of assessing sympathetic activity in various tissues by direct measurement of the noradrenaline turnover rate may be applied to the study of the adrenergic nervous system in the physiology and pathophysiology of the gastrointestinal tract.