Separation of the gut hormone endocrine-cell storage granules of human jejunum using analytical subcellular fractionation.

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Abstract
Analytical subcellular fractionation techniques in combination with specific radioimmunoassays have been used to investigate the properties of the hormone-containing granules in human jejunal biopsy specimens. After gentle homogenisation, for all hormones except VIP, over 90% of the immunoreactivity was released in intact granules into the post-nuclear supernatant. Approximately 50% of the VIP immunoreactivity sedimented with the low speed pellet, probably reflecting the presence of this peptide in nerve fibres. The following hormone granules (equilibrium densities between parentheses) were separated by isopycnic centrifugation on the sucrose density gradients: VIP (1 x 17), motilin (1 x 20), and secretin (1 x 24). Gastrin and GIP granules were not resolved, both having the same modal density of 1 x 22 g/cm3. This combination of procedures thus provides a new quantitative technique for studying the properties of the gastrointestinal hormone-containing granules, and should therefore be of value in investigating pathophysiological problems in a variety of gastrointestinal diseases.