Article date: April 1978
By: MARTINE AGGERBECK, GEORGES GUELLAEN, JACQUES HANOUNE in Volume 62, Issue 4, pages 543-548
Labetalol (AH 5158A) inhibited the adrenaline‐stimulated adenylate cyclase activity of rat liver and heart. This drug had no effect on basal or guanosine triphosphate (GTP)‐activated adenylate cyclase activities.
Labetalol displaced the binding of the specific ligands [3H]‐dihydroergocryptine and (—)‐[3H]‐dihydroalprenolol from their respective α and β‐adrenoceptors in rat heart and liver. The affinity of labetalol was 10 fold higher for the β‐ than for the α‐adrenoceptor. It appeared to be 10 to 100 times less potent than phentolamine in blocking α‐adrenoceptors and 5 to 10 times less potent than propranolol in blocking β‐receptors.
It is concluded that labetalol exerts its dual α‐ and β‐antagonism by acting directly on the plasma membranes, where it binds competitively to α‐ and β‐adrenoceptors.
Labetalol (AH 5158A) inhibited the adrenaline‐stimulated adenylate cyclase activity of rat liver and heart. This drug had no effect on basal or guanosine triphosphate (GTP)‐activated adenylate cyclase activities.
Labetalol displaced the binding of the specific ligands [3H]‐dihydroergocryptine and (—)‐[3H]‐dihydroalprenolol from their respective α and β‐adrenoceptors in rat heart and liver. The affinity of labetalol was 10 fold higher for the β‐ than for the α‐adrenoceptor. It appeared to be 10 to 100 times less potent than phentolamine in blocking α‐adrenoceptors and 5 to 10 times less potent than propranolol in blocking β‐receptors.
It is concluded that labetalol exerts its dual α‐ and β‐antagonism by acting directly on the plasma membranes, where it binds competitively to α‐ and β‐adrenoceptors.
DOI: 10.1111/j.1476-5381.1978.tb07759.x
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