Vasoactive intestinal peptide: quantification by radioimmunoassay in isolated cells, mucosa, and muscle of the hamster intestine.

Vasoactive intestinal peptide (VIP) levels were quantified by radioimmunoassay in three strata of hamster bowel wall, namely, epithelial cells isolated by a vibration technique, scrapings of the vibrated intestine, and in the remaining muscle. Expressed on a wet weight basis, highest levels of the peptide (as a percentage of total bowel wall content) were found in the muscle (72%) followed by high levels in scrapings of denuded villi (27%). Villus and crypt epithelial cells, isolated as one fraction, contained very low levels (less than 1%) of total VIP. To correct for differences in water content of the various strata, data were also calculated on the basis of tissue protein. When expressed in this manner, scrapings of denuded villi and the remaining muscle, both areas of dense autonomic innervation, were virtually equal in their VIP content (mean +/- SE, 9.5 +/- 4 and 11 +/- 2 ng per mg of protein, respectively). However, the VIP concentration of the cells was over two orders of magnitude less than the muscle or scrapings of denuded villi (0.02 +/- 0.007 ng per mg of protein). These results suggest that VIP is concentrated with or near the neural elements of the gut.