Responses to Noradrenaline and Potassium, and Disposition of Noradrenaline in Aortic Strips of Desoxycorticosterone Acetate – NaCl Hypertensive Rabbits

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Abstract
The responses of aortic strips to low concentrations of noradrenaline (3 × 10−10, 1 × 10−9, and 3 × 10−9 g/ml) were enhanced in rabbits made hypertensive by desoxycorticosterone acetate (DOCA)–NaCl. However, contractions of equivalent magnitude produced by potassium were depressed. No augmentation of responses to noradrenaline was observed if the strips were maintained under 5 rather than the standard 2 g tension. Experiments utilizing the oil-immersion technique, to eliminate diffusion of drug into the bathing medium, revealed that there was no difference in the ability of aortic strips from normotensive and hypertensive rabbits to inactivate noradrenaline (1 × 10−8 g/ml). Also, the role of catechol-O-methyl-transferase in terminating the action of this amine did not differ in strips obtained from untreated and DOCA–NaCl treated rabbits. It is concluded that enhanced responses of aortic strips to noradrenaline in hypertension are not explicable on the basis of an alteration in amine metabolism.

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