Alpha-adrenergic receptors in the regulation of liver functions

Rat liver contains 80% alpha 1 and 20% alpha 2 receptors. The role of adrenergic regulation of liver functions was studied by administration of antagonist and agonist pharmaca. Female rats were treated with the selective alpha 1 receptor blocker prazosin. A transitory inhibition of microsomal monooxygenases was observed after 5 days which was terminated at the 12 day. A 18.7% loss of glycogen was measured at this time indicating a slight adrenergic glycogenolytic effect. Dihyd 50-ergocryptime an equal lebocker of alpha 1 alpha 2 receptori preserved glycogen content and has not impaired liver functions. Agonist epinephrine inhibited monooxygenase functions and mobilised 75% of hepatic glycogen. Simultaneous administration of prazosin with epinephrine resulted into glycogen loss due to alpha 2 receptor stimulation. Dihydroergocryptine antagonised rather the metabolic actions of epinephrine. We have established that alpha 2 receptors are also involved in hepatic carbohydrate metabolism.