The influence of vasoactive intestinal peptide receptors in dispersed acini from rat submandibular gland on cyclic AMP production and mucin release.

Vasoactive intestinal peptide has been identified as an important regulator of submandibular salivary gland function, consistent with its localization with acetylcholine in parasympathetic neurones innervating this gland. Enzymatically dispersed acini from rat submandibular gland are a useful system in which to study gland regulation at the cellular level. Here, three aspects of vasoactive intestinal peptide interactions with acini were examined: inhibition of binding of [125I]-vasoactive intestinal peptide, stimulation of cyclic AMP production and enhancement of mucin release. Vasoactive intestinal peptide and peptide histidineisoleucineamide inhibited [125I]-vasoactive intestinal peptide binding to intact acini, with IC50 values of 16 +/- 3 and 46 +/- 17 nM, respectively. This rank order of potency agrees with that observed previously in assays using rat submandibular gland membranes and is similar to values obtained in assays measuring increases in cyclic AMP production in which the ED50 values for vasoactive intestinal peptide and peptide histidineisoleucineamide were 3.1 +/- 1.8 and 29 +/- 13 nM, respectively. Although vasoactive intestinal peptide stimulation of cyclic AMP production was only about 10% of that seen in response to isoproterenol, the levels of mucin release induced by the two agents were more similar. The ED50 for vasoactive intestinal peptide-stimulated mucin release was 0.12 +/- 0.05 nM, thus suggesting an activation anomaly in the vasoactive intestinal peptide receptor-coupled signal transduction pathway at a point between cyclic AMP production and mucin release.