Effects Op Vasopressin and Angiotensin Ii on Vascular Pressures in Conscious Dogs

Abstract

In the last century the pituitary substance later identified as vasopressin was discovered by means of its effect on mean arterial blood pressure (Oliver & Schsfer, 1895). Nevertheless the physiological significance o f the vasoactive properties of vasopressin remains undetermined (Bartter, 1981). Recent studies (Malayan et al. 1980; Montani et al. 1980) demonstrate that vasopressin affects cardiovascular homeostasis in doses much smaller than previously believed. In the present study effects of exogenous arginine vasopressin on arterial and central venous blood pressures in conscious trained dogs were investigated and compared with the results of administration of similar amounts of angiotensin 11. In addition studies of the effects of combined infusions of the hormones were performed. Methods.Experiments were performed on seven dogs (10.5-15.2 kg) which were fed on commercial dog food (Lats-Purina) supplying them with average intakes of sodium and potassium of 7.8 and 9.0 mmol/d per kg body weight, respectively. Prior to the experiments the dogs were surgically prepared with bilateral carotid loops in order to facilitate arterial puncture and trained to stand in the laboratory for hours loosely supported by a canvas sling. Experiments were performed after 18 h af fasting. Sterile disposable catheters were placed percutaneously in a common carotid artery, in the right atrium, and in a saphenous vein. The latter catheter was used for infusion of hormone(s) dissolved in isosmotic glucose solution. Systolic, mean, and diastolic arterial pressures and right atrial pressure were recorded by an U.V. recorder via Statham transducers.Hormones were infused for 30 min. Pressures were recorded continuously from lo min before to lo min after the infusion. Blood samples were obtained at regular intervals and plasma was analyzed for sodium, potassium, and vasopressin. The latter was measured by radioimmunoassay. The experiments included infusions of hormones at the following rates: 48