ADRENERGIC RECEPTORS IN RAT LIVER

Abstract

Specific alpha and beta adrenergic agonists, phenylephrine and isoproterenol, were applied to liver perfusion system. Both agonists stimulated the rate of gluconeogenesis from lactate in normal liver; however, only phenylephrine was effective in hypothyroid liver. The crossover point in the metabolite profile was between pyruvate and phosphoenolpyruvate. Pyruvate carboxylase activity was activated by both agonists in the normal liver, while phenylephrine only activated pyruvate carboxylase in hypothyroidism. In contrast to pyruvate carboxylase, the activity of PEP carboxykinase did not change even in the presence of adrenergic agonists. It is therefore considered that thyroid hormone may be required for the stimulation by isoproterenol, whereas the function stimulated by phenylephrine is independent of thyroid hormone. Gluconeogenesis from lactate is thus activated with addition of phenylephrine even in a hypothyroid condition.