Aldosterone Response to Angiotensin Blockade in the Conscious Sodium-Depleted Rabbit

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Abstract
To evaluate the role of the renin-angiotensin [A] system in the aldosterone response to Na depletion in the conscious rabbit, angiotensin blockade was achieved with [Sar1, Ala8] AII and SQ 20881 [teprotide]. After infusion of [Sar1, Ala8] AII (1 .mu.g/kg per min) for 60 min into Na-depleted animals, PAC [plasma aldosterone concentration] was unchanged (33.3 .+-. 7.4 ng% compared with a control Na-deplete value of 41.1 .+-. 8.2 ng%). When the dose was increased to 50 .mu.g/kg per min for an additional 60 min, PAC fell to 15.4 .+-. 3.7 ng% (P < 0.0125), a value similar to the Na replete value. In a 2nd group of animals, SQ 20881 was given initially as a 7 mg/kg bolus and followed by an infusion of 60 .mu.g/kg per min for 30 min; PAC fell from a Na-deplete level of 86.6 .+-. 21.0 to 63.9 .+-. 18.2 ng% (P < 0.025). The infusion was extended to 60 min in 5 of the 7 animals and PAC remained significantly reduced (63.3 .+-. 16.2 ng%, P < 0.01). Attenuation of the aldosterone response to Na depletion occurred with both [Sar1, Ala8] AII and SQ 20881 in the conscious rabbit, indicating a role for the renin-A system in this model.