Fate of noradrenaline storage vesicles after release

Using [(3)H]noradrenaline (NA), changes in vesicular NA content and storage capacity of rat heart ventricles resulting from 24 h cold stress have been measured. NA content was decreased to 63% of control value; uptake of [(3)H]NA was the same in control and cold treated animals, while NA storage capacity was decreased to 78% of control value. This suggests that vesicles are not immediately available for re-use after NA release. After cold stress the degree of saturation of the vesicular storage capacity was reduced to 78% of control value, suggesting a change in the balance of NA synthesis and storage.