Interaction of Angiotensin II with Noradrenaline and Other Spasmogens on Rabbit Isolated Aortic Strips

Angiotensin II in sub-contractor concentrations enhanced the contractions of rabbit isolated aortic strips to noradrenaline, potassium chloride, histamine, acetylcholine, isoprenaline and 5HT. The potentiation of noradrenaline responses by angiotensin II was independent of any effect of angiotensin II on neuronal uptake of noradrenaline. The sensitization of this tissue to spasmogens induced by angiotensin II occurred in reserpine-treated preparations and in normal tissues suspended in calcium-free bathing medium. Procedures which abolished the transfer of sodium ions across membranes such as substitution of fructose for glucose in the bathing medium, absence of potassium ions or treatment with ouabain each abolished the non-specific sensitization. The evidence suggests that angiotensin II may cause a non-specific sensitization of this tissue by inhibiting sodium transfer across the cell membrane.