Analysis of somatostatin peptides produced by an endocrine pancreatic cell line

Biological active forms of somatostatin are produced by cleavage of large precursors. If the sequence of the pre-proform of somatostatin has been deduced from cDNA structure in several species, little is known about the processing of these large precursors. For this purpose, the analysis of immunoreactive components secreted by the R.I.N. cell line was investigated. After selection of a cell population and culture conditions providing the optimal production of these peptides, analysis of their molecular forms was done by molecular gel filtration. The results show that mainly pro-forms accumulate in the culture medium while besides the pre-proform the smaller immunoreactive species behaving like S-28 and S-14 were found in cell extracts. Incorporation studies in serum free medium showed rapid formation of an intermediate compound eluted at 1.87 V0.