Effect of Equi‐pressor Doses of Synthetic α‐ and β‐Angiotensin II on Urinary Volume and Urinary Electrolytes in Normotensive Subjects

Abstract

3-Asp1-Va16-Angiotensin I1 differs from a-Asp1-Va15-Angiotensin 11 in molecular structure solely in the respect that the asparaginic acid is bonded to arginine in the p instead of the a position. The principal difference in the pharmacological properties of the two angiotensins has been found in their vasopressor effect. This effect of 1-angiotensin I1 clearly exceeds that of a-angiotensin I1 (3).In the present study the effect of pangiotensin I1 and a-angiotensin I1 on diuresis and on the urinary excretion of sodium and potassium was followed under conditions in which the vasopressor response to the angiotensins was equally strong. Material and methodsThe series consisted of 10 normotensive women 2 1 to 59 years of age. No cardiovascular or renal disease had been diagnosed previously or a t the time of the test. The subjects had fasted for 10 hours, and 1 1/2 hours before the test was begun they drank about 1 litre of water. The bladder was emptied by a catheter, which remained in the bladder throughout the test. The experiment lasted 150 min., divided into five successive periods of 30 min. each. During each period the amount of urine excreted into the bladder was measured and the urinary sodium and potassium were determined by flame photometry. The mean urinary volumes and mean urinary sodium and potassium values of the first two periods were used as initial values. Immediately after the second period P-angiotensin I1 was injected intramuscularly in a n amount sufficient to raise the systolic and diastolic blood pressures 20-30 m m Hg above the initial levels. T h e dose of /3-angiotensin I1 required to attain this vasopressor effect had been determined on the preceding day. The product used was P-Asp1-Va15-Hypertensin I1 (Ciba 33902-Ba) developed by the Ciba Laboratories. Blood-pressure measurements were made at 5 min. intervals until the pressor reverted to the initial level. The test was repeated on the same subjects on the following day with the difference that during period I11 a-Asp'-amide-Angiotensin