Binding and uptake of [3H]adrenaline by perfused rat liver

The binding and uptake of [3H]adrenaline by the intact perfused rat liver was investigated. We showed that the administration of [3H]adrenaline to liver resulted in the rapid uptake of the radioligand, and that such uptake was independent of any Ca2+ redistributions induced by the hormone. At low adrenaline concentrations (less than 50 nM) uptake was inhibited by prazosin, whereas at higher hormone concentrations a significant proportion of total [3H]adrenaline uptake could not be inhibited by this antagonist. [3H]Adrenaline uptake could be directly correlated with adrenaline-induced responses such as an increased rate of respiration and glycogenolysis. The partial inhibition (approx. 25%) of [3H]adrenaline uptake by antagonists was sufficient for the total inhibition of hormone-induced responses. The effect of various pharmacological agents on [3H]adrenaline uptake was investigated, and the contribution of tissue-related factors to alpha-adrenergic agonist-antagonist interactions in vivo is discussed.