COOH-terminally extended secretins are potent stimulants of pancreatic secretion.
Posttranslational processing of preprosecretin generates several COOH-terminally extended forms of secretin and alpha-carboxyl amidated secretin. We used synthetic canine secretin analogs with COOH-terminal -amide, -Gly, or -Gly-Lys-Arg to examine the effects of COOH-terminal extensions of secretin on bioactivity and detection in RIA. Synthetic products were purified by reverse-phase and ion-exchange HPLC and characterized by reverse-phase isocratic HPLC and amino acid, sequence, and mass spectral analyses. Secretin and secretin-Gly were noted to coelute during reverse-phase HPLC. In RIA using eight different antisera raised against amidated secretin, COOH-terminally extended secretins had little or no cross-reactivity. Bioactivity was assessed by measuring pancreatic responses in anesthetized rats. Amidated canine and porcine secretins were equipotent. Secretin-Gly and secretin-Gly-Lys-Arg had potencies of 81 +/- 9% (P > 0.05) and 176 +/- 13% (P < 0.01), respectively, compared with amidated secretin, and the response to secretin-Gly-Lys-Arg lasted significantly longer. These data demonstrate that 1) amidated secretin and secretin-Gly are not separable under some chromatographic conditions, 2) current RIA may not detect bioactive COOH-terminally extended forms of secretin in tissue extracts or blood, and 3) the secretin receptor mediating stimulation of pancreatic secretion recognizes both amidated and COOH-terminally extended secretins.
Solomon
T E
TE
CURE: Digestive Diseases Research Center, Greater Los Angeles Department of Veterans Affairs Health Care System, Los Angeles 90073, USA. solomont@ucla.edu
Walsh
J H
JH
Bussjaeger
L
L
Zong
Y
Y
Hamilton
J W
JW
Ho
F J
FJ
Lee
T D
TD
Reeve
J R
JR
D000595:Amino Acid Sequence; D000818:Animals; D004285:Dogs; D007275:Injections, Intravenous; D008297:Male; D008969:Molecular Sequence Data; D010179:Pancreas / Q000187:drug effects / Q000378:metabolism*; D010189:Pancreatic Juice / Q000187:drug effects / Q000378:metabolism*; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D011498:Protein Precursors / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D051381:Rats; D017207:Rats, Sprague-Dawley; D012633:Secretin / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*
D010455:Peptides; D011498:Protein Precursors; C065605:prosecretin; D012633:Secretin