Intravenous administration of atriopeptin III affects arterial blood pressure differentially in young and old male rats.

The effects of intravenous administration of various doses of atriopeptin III (0.4-36 nmol kg-1) on arterial blood pressure, urinary flow and Na+ and K+ excretion were analysed in awake animals. A dose-related reduction of arterial blood pressure was obtained in 4- and 24-month-old unrestrained, freely moving male rats. A dose-related increase in the diuresis and in sodium and potassium excretion was present in both young and old rats. The hypotensive action was significantly prolonged in the aged animals, indicating possible alterations in the control of the cardiovascular system by the endocrine activity of the heart in the old animal.