Stimulating ADH secretion: the importance of cardiac permeability and reflex
With a decrease in blood volume, the concentration of ADH rapidly increases. Thus, with a severe decrease in blood volume, cardiac reflexes play an important role in stimulating ADH secretion.
Cardiac permeability and reflex stimulate ADH secretion
As shown in the figure, either a decrease in blood volume or an increase in extracellular fluid osmotic pressure stimulates ADH secretion. However, ADH is significantly more sensitive to small changes in osmotic pressure than changes with a similar percentage in blood volume. For example, a change in plasma osmolality of only 1% is sufficient to increase ADH concentrations. In contrast, after blood loss, plasma ADH concentrations do not change significantly until blood volume is decreased by about 10%. With a further decrease in blood volume, the concentration of ADH rapidly increases. Thus, with a severe decrease in blood volume, cardiac reflexes play an important role in stimulating ADH secretion.
Figure. The effect of an increase in plasma osmolality or a decrease in blood volume to the plasma concentration (P) of antidiuretic hormone (ADH), also known as arginine vasopressin (AVP).
Board. Control ADH secretion
The usual adjustment of ADH secretion in simple dehydration is done mainly by changes in plasma osmolality. A decrease in blood volume, however, greatly increases the ADH response to an increase in osmotic pressure.
Other ADH-secreting stimuli
ADH secretion can also be increased or decreased by other stimuli to the central nervous system, as well as by various drugs and hormones, as shown in the table. For example, nausea is a powerful stimulus for the release of ADH, which can rise up to 100 times normal after vomiting. Additionally, drugs like nicotine and morphine stimulate the release of ADH, while some drugs, such as alcohol, inhibit ADH release. The apparent urination that occurs after drinking alcohol is partly due to the inhibition of ADH release.