THE EXCRETION of water is influenced by many factors. One of the most important factors is the antidiuretic hormone of the posterior lobe of the pituitary gland (ADH). An increase in the osmotic activity of the blood increases the secretion of antidiuretic hormone and results in a concentrated urine.1 Drugs and reflex stimuli also release the antidiuretic hormone.2 A decreasing osmotic activity of the blood inhibits the release of the antidiuretic hormone, and a water diuresis follows.
Small intravenous doses of vasopressin injection (pitressin®) in man produce the same effect on the excretion of water and salt as does endogenously produced vasopressin. Both act by increasing the tubular absorption of water without altering glomerular filtration or renal blood flow; neither have demonstrated in short-term experiments a striking effect on excretion of sodium chloride.3 In water-loaded subjects administration of vasopressin may cause a slight decrease in the excretion