Lysine Vasopressin

Lysine vasopressin is a nonapeptide hormone secreted by the neurons of the supraoptic and paraventricular nuclei of the hypothalamus. Its structure is similar to oxytocin, except that it contains lysine at the 8th amino acid position, whereas oxytocin has leucine at this position. This structural difference gives lysine vasopressin unique physiological functions.

Physiological Functions:

Regulation of Water Metabolism:

The primary role of lysine vasopressin is to increase the permeability of the distal convoluted tubules and collecting ducts to water, promoting water reabsorption. This reduces urine production, concentrates urine, and maintains the body's water balance. When the body is dehydrated, the hypothalamus increases the secretion of lysine vasopressin, enhancing water reabsorption in the kidneys and reducing urine output. Conversely, when there is excess water in the body, the secretion of lysine vasopressin decreases, leading to increased urine output.

Vasoconstrictive Effects:

Lysine vasopressin causes constriction of small arteries and capillaries, leading to an increase in blood pressure. In emergency situations such as severe blood loss, the increased secretion of lysine vasopressin results in peripheral vasoconstriction and elevated blood pressure, helping to maintain blood perfusion to vital organs.

Clinical Applications:

Treatment of Diabetes Insipidus:

Diabetes insipidus is a condition caused by insufficient secretion of lysine vasopressin due to hypothalamic-neurohypophyseal dysfunction or renal insensitivity to lysine vasopressin. This leads to impaired water reabsorption in the renal tubules, resulting in symptoms such as polyuria and polydipsia. Lysine vasopressin is used to treat central diabetes insipidus by promoting water reabsorption in the kidneys, reducing urine output, and alleviating symptoms.

Control of Bleeding:

In cases of bleeding caused by surgery or trauma, lysine vasopressin can be used to constrict blood vessels and reduce local blood flow, achieving hemostasis. For example, in cases of esophageal variceal bleeding, intravenous infusion of lysine vasopressin can constrict blood vessels, reduce portal pressure, and control bleeding.

Diagnosis of Pituitary Function:

By administering exogenous lysine vasopressin and observing the body's response, pituitary function can be assessed. For instance, the lysine vasopressin test involves comparing changes in urine output and urine osmolality before and after injection, helping to diagnose conditions such as hypopituitarism.