What effect does hypotonic fluid and hypertonic solution have on ADH secretion?
The intake of hypotonic fluids leads to a decrease in ADH secretion, the intake of hypertonic fluids leads to an increase in ADH secretion.
The tonicity of a cell is the ability of the surrounding fluids to cause the cell to gain or lose water. Tonicity depends on the concentration of solutes that cannot cross the membrane relative to that inside the cell. When the fluid is hypotonic, it will have less of these solutes, and water will move into the cell. When the fluid is hypertonic, it will have more solutes and water will move out of the cell. When the fluid is isotonic, cell and fluid will have an equal concentration of solutes and no net water movement will occur.
ADH, Antidiuretic Hormone, or vasopressin, is a hormone in the regulatory circuitry of the kidney that regulates the osmolarity of the blood.
When blood osmolarity rises, such as after a meal, and it rises above the set point of 300 mOsm/L, ADH release into the bloodstream increases. This ADH targets the epithelial cells of the collecting ducts in the kidney. This makes the epithelial cells more permeable to water, which concentrates the urine, lowers urine volume, and reduces blood osmolarity back to the set point.
Blood osmolarity is, therefore, influenced by food and fluid intake. When a hypotonic fluid or solution is consumed, blood osmolarity decreases, which leads to a decrease in ADH secretion. When a hypertonic fluid or solution is consumed, blood osmolarity increases, and, therefore, ADH secretion increases.
Source: Campbell & Reece’s Biology 10th edition