Influences of propranolol on uptake and loss of norepinephrine in tissues of rats

Propranolol 12.5 mg/kg was injected sc bid for 2 or 9 d in rats. The uptake rate of [3H]norepinephrine ([3H]NE) was markedly accelerated in the heart, spleen, lungs, and adrenal glands. The enhancements ranged from 182 to 285% and sustained throughout the period of medication. The releasing rate constant K of [3H]NE in these tissues increased in the d-2 group. The K values of lungs and spleen decreased in the d-9 group. Both the uptake rate and releasing rate constant K showed a sharp fall on the d 2 after the withdrawal of propranolol to or below the control. Chronic medication of propranolol in rats exerted significant effects on the uptake and releasing rate constants in the tissues.