Effect of adrenergic agents on responses of smooth muscle to angiotensin

¹ Research Division, The Cleveland Clinic Foundation, Cleveland, Ohio

Evidence has been presented previously indicating that angiotensin acts indirectly on guinea pig intestines by stimulating the ganglion cells of Auerbach's plexus. Further studies have shown that the adrenergic nerves are not directly involved in this mechanism, although adrenergic blocking agents suppress the response to angiotensin, probably by acting directly on the cell membrane. Epinephrine, and to a lesser extent norepinephrine and isoproterenol, inhibited the contraction of ileum and uterus to angiotensin, and to electrical stimulation, possibly by reversing or blocking sodium or potassium ion flux across the cell membrane resulting from the action of the peptide. Most of the adrenergic blocking agents studied, with the exception of Dibenamine, also inhibited the response to angiotensin. Reserpine, guanethidine, and bretylium block its action, possibly by releasing catecholamines from bound tissue stores, and phentolamine and piperoxane, by their sympathetic actions imitating the catecholamines.

Note:
With the Technical Assistance of Cornelia L. Brand