Role of adrenergic receptors in the mechanism of action of catecholamines and DOPA on proliferative processes

: Catecholamines (adrenaline, isoproterenol) and L-DOPA decreased the mitotic index of L-cells in culture. The action of catecholamines was blocked by the beta-adrenergic antagonist propranolol, but was not abolished by the alpha-adrenoblocker phenoxybezamine. The L-DOPA-induced decrease in the mitotic index did not depend on the pretreatment with the adrenoblockers. Catecholamines inhibited the incorporation of 3H-thymidine and 3H-leucine into DNA and total protein of the cells, respectively. Preincubation of the culture with propranolol for 10-20 minutes before catecholamine administration prevented the action of catecholamines. Phenoxybenzamine, an alpha-adrenoreceptor blocker, did not produce such an effect. The data obtained point to the leading role of beta-adrenoreceptors in the mechanism of the effects of catecholamines on proliferative processes. The action of L-DOPA on cell proliferation does not seem to be linked with adrenoreceptor activation.