VIP is a peptide hormone containing 28 amino acid residues.
Its role in the intestine is to greatly stimulate secretion of water and electrolytes, as well as dilating intestinal smooth muscle, dilating peripheral blood vessels, and inhibiting gastrin-stimulated gastric acid secretion.
It is also found in the brain and some autonomic nerves.
It has a half-life in the blood of about 2 minutes.
