**7. Effect of ethanol on antidiuretic hormone (vasopressin)**

Vasopressin is an antidiuretic hormone that plays a major role in the regulation of water excretion. The posterior pituitary gland releases vasopressin in response to a fall in blood volume or a rise in plasma osmolality and acts to conserve water by increasing the permeability of water to the distal convoluted tubules and collecting tubules in the renal nephrons through insertion of aquaporin-2 channels into the apical membrane of the tubular epithelial cells [44]. Ingestion of alcohol does increase plasma osmolality, but alcohol also acts directly to inhibit the release of vasopressin, independent of plasma osmolality. Once ethanol is consumed, it is distributed in the blood, brain and muscle tissues. Alcohol is a diuretic that affects five centers in the brain namely the cerebral cortex, limbic system, cerebellum, hypothalamus and pituitary gland and the medulla. The hypothalamus controls the automatic functions of the brain and coordinates endocrine functions through nerve impulse actions on the pituitary gland. Ethanol affects hypothalamus and pituitary gland by increasing urine excretion; inhibiting the pituitary secretion of anti-diuretic hormone (ADH), which makes the kidney reabsorb water. When the ADH levels are decreased, the kidney does not reabsorb water from the urine which results in the kidney producing more urine.
