Noradrenaline concentrations in gut muscle and mucosa of the copper-deficient steer and rat.

1. Noradrenaline (NA) concentrations in the duodenum and colon of copper-deficient and Cu-adequate steers and rats were determined. 2. In Cu-deficient steers exhibiting diarrhoea, there were significant decreases (P less than 0.05) in duodenal and colonic muscle NA concentrations. Duodenal and colonic mucosal NA concentrations in the steer were also diminished by Cu deficiency but this effect was not statistically significant. 3. Rat intestinal musculature had a higher NA concentration than that of the steer. Rat duodenal muscle NA was not influenced by Cu deficiency, but increased markedly with age. 4. It is suggested that the decline in NA concentration of cattle musculature in copper deficiency may have a role to play in the aetiology of diarrhoea in such animals.