Processing and secretion of prosomatostatin by the pig pancreas

Antisera and radioimmunoassays against five different regions of prosomatostatin (proSS) were used for chromatographical analysis and for immunohistochemical mapping of the products of proSS in the pig pancreas. Secreted products of proSS were studied by analysis of effluent from isolated perfused pig pancreas obtained during isoproterenol stimulation. All cells that were stained with one antiserum also stained with the other antisera. Immunoreactive nerves were not observed. Isoproterenol increased equally the secretion of proSS 20-36, proSS 65-76, and proSS 79-92 immunoreactivity. The major molecular forms identified in pancreatic extracts and released from the pancreas were proSS 79-92; proSS 65-76; an N-terminally extended form of proSS 65-76; and two larger forms comprising the proSS 20-36 sequence (but not the 1-13 sequence) with and without the proSS 65-76 sequence. ProSS 1-10, 1-32 and 65-92 (somatostatin 28) were not identified.