everything that disturbs the homeostatic balance of the body can be defined as stress and any stress factor activating the hypothalamic- pituitary-adrenal (HPA) axis causes an increase in arginine vasopressin (AVP) plasma concentrations.
AVP is a 9 amino acid peptide in the ring structure and derived from pre-pro vasopressin. Pre-pro vasopressin is a pro hormone that synthesized by supraoptic nucleus of hypothalamus and reaches neurohypophysis by moving along axons along in neurosecretory granules. This prohormone is segmented in a result of a cascade of four hydrolytic enzymes during its axonal transport to neurohypophysis: 1-AVP 2-neurophysin II 3-copeptin 4- signal peptide
AVP: this hormone is the most important hormone in regulation of body osmotic balance y regulation of water reabsorption from kidneys. Main stimulators of secretion of AVP are dehydration or increasing in plasma osmolality and decreased blood flow. The other stimulators of AVP secretion are pain, stress ,sleeping and chemical factors like catecholamines and angiotensin II.
this hormone has three types of receptors: V1a, V1b, V2. The commonly known target tissues for vasopressin are kidneys and vascular smooth muscle cells. But vasopressin receptors are expressed in a number of other organs and tissue
copeptin: a 39-aminoacid glycopeptide is a c-terminal part of pre-pro vasopressin. The main function role in the circulation is still unknown. Normal value of copeptin is 1.7-11.25 pmol/L. the normal concentration is more in men when compare to women and has not correlation with age or glomerular filtration rate in healthy individuals. Because, copeptin released in circulation in the same amount with AVP, its value reflects AVP production. Since its half-life is higher than AVP, it can be used as a substitute for AVP measurement.