Role of vasopressin in blood pressure regulation in conscious water-deprived dogs

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Abstract
The role of vasopressin in the regulation of blood pressure during water deprivation was assessed in conscious dogs with 2 antagonists of the vasoconstrictor activity of vasopressin. In water-replete dogs, vasopressin blockade caused no significant changes in mean arterial pressure, heart rate, plasma renin activity (PRA) or plasma corticosteroid concentration. In the same dogs following 48-h water deprivation, vasopressin blockade increased heart rate from 85 .+-. 6 to 134 .+-. 15 beats/min (P < 0.0001), increased cardiac output from 2.0 .+-. 0.1 to 3.1 .+-. 0.1 l/min (P < 0.005), and decreased total peripheral resistance from 46.6 .+-. 3.1 to 26.9 .+-. 3.1 U (P < 0.001). Plasma renin activity increased from 12.4 .+-. 2.2 to 25.9 .+-. 3.4 ng ANG I.cntdot.ml-1.cntdot.3 h-1 (P < 0.0001) and plasma corticosteroid concentration increased from 3.2 .+-. 0.7 to 4.9 .+-. 1.2 .mu.g/dl (P < 0.05). Mean arterial pressure did not change significantly. When the same dogs were again deprived of water and pretreated with the .beta.-adrenoceptor antagonist propranolol, the heart rate and PRA responses to the antagonists were attenuated, and mean arterial pressure decreased from 103 .+-. 2 to 91 .+-. 3 mmHg (P < 0.001). Vasopressin plays an important role in blood pressure regulation during water deprivation in conscious dogs.