THE RELEASE OF SOMATOSTATIN-14 FROM HUMAN SUBMUCOSAL GANGLIA IN TISSUE-CULTURE

A dispersed culture of cells from the submucous plexus of the human small intestine has been developed to examine the localization, release, and molecular characteristics of somatostatin immunoreactivity. Forty percent of the submucosal neurones per ganglion in tissue sections and 35% of cells per group of cells in culture contained somatostatin immunoreactivity. Acetic acid extracts of cultures contained 1990 +/- 809 pg somatostatin immunoreactivity/10(6) cells. Incubation of cultures with phorbol 12-myristate 13-acetate (beta PMA), an activator of protein kinase C, at concentrations up to 10(-6) M for 120 min increased the release of somatostatin immunoreactivity by up to 23 times the basal level, and up to 27 times the basal level when extracellular K+ was increased from 5 to 10 mM. Of the total somatostatin immunoreactivity released in response to beta PMA (10(-6) M, 10 mM K+), 59% was present in the medium after 30 min and 80 % after 60 min. Basal release of somatostatin immunoreactivity could be reliably measured only after 120 min. The release of somatostatin immunoreactivity by beta PMA was not due to nonspecific membrane effects, since the inactive 4 alpha-phorbol at the same concentrations did not alter basal release. Greater than 90 % of somatostatin immunoreactivity present in acid extracts of cultures and released by beta PMA eluted with the same retention time as synthetic somatostatin-14 on reverse-phase high-performance liquid chromatography.