Tissue distribution of vasoactive intestinal peptide (VIP)-containing nerves and their target cells were studied in labial salivary glands in patients with Sjögren's syndrome and in healthy controls.
Immunoperoxidase staining was used to demonstrate VIP-containing nerve fibers, and receptor autoradiography with 125I-Bolton Hunter (BH)-VIP was used to demonstrate VIP positive binding sites.
VIP-containing nerves were seen around salivary acini, salivary ducts, blood vessels and deep parenchyma, but were absent from large inflammatory cell foci in patients with Sjögren's syndrome. Receptor autoradiography with 125I-BH-VIP disclosed VIP binding sites on mucous acinar cells and blood vessels, whereas salivary ducts contained no VIP receptors. VIP binding sites were also absent from the centers of large inflammatory cell foci/acinar atrophy.
The topology of VIP and its receptor suggests that VIP may act on the vascular and secretory components of the salivary gland. However, VIP causes only a slight increase in non-adrenergic, non-cholinergic salivary secretion. It is therefore more likely that this extensive tissue distribution of VIP and its receptors reflects its recently suggested trophic effects on salivary gland tissue. This is further supported by the observation that VIP-IR nerves/VIP binding sites were absent in areas of focal lymphocytoid infiltrates/acinar atrophy in patients with Sjögren's syndrome.