Abstract

Vasoactive intestinal peptide (VIP), first isolated from the gut, was originally considered a candidate gastrointestinal hormone. Since about 1975, however, it has become increasingly clear that it is primarily a neurotransmitter or neuromodulator and that it exerts its functions mainly by local release from nerve endings. VIP plays a hormonal role only when it is released in large amounts from a tumor, with a consequent overflow into the circulation and grossly elevated plasma concentrations of the peptide. Moderately increased VIP plasma and tissue concentrations that cause mainly local effects are found in intestinal ischemia. Crohn's disease and some other chronic inflammatory diseases of the bowel. VIP is also measured in increased amounts in the normal fetus and neonate, where it may play an important physiological role. Such an increase of VIP levels in the circulation could enhance perfusion and metabolic activity of tissues during their rapid-growth period. On the other hand, disorders with a disturbed VIP function such as achalasia and Hirschsprung's disease and possibly also asthma and cystic fibrosis seem to be characterized mainly by a derangement of smooth muscle activity and/or exocrine secretion. Considering this list of disorders where VIP has either a proven or suspected role, it is easy to imagine the significance of this peptide in pediatric pathophysiology.