Secretin (Porcine)

Secretin-enhanced MRCP (S-MRCP) has advantages over standard MRCP for imaging of the pancreaticobiliary tree. Through the use of secretin to induce fluid production from the pancreas and leveraging of fluid-sensitive MRCP sequences, S-MRCP facilitates visualization of ductal anatomy, and the findings provide insight into pancreatic function, allowing radiologists to provide additional insight into a range of pancreatic conditions. This narrative review provides detailed information on the practical implementation of S-MRCP, including patient preparation, logistics of secretin administration, and dynamic secretin-enhanced MRCP acquisition. Also discussed are radiologists' interpretation and reporting of S-MRCP examinations, including assessments of dynamic compliance of the main pancreatic duct and of duodenal fluid volume. Established indications for S-MRCP include pancreas divisum, anomalous pancreaticobiliary junction, Santorinicele, Wirsungocele, chronic pancreatitis, main pancreatic duct stenosis, and assessment of complex postoperative anatomy. Equivocal or controversial indications are also described along with an approach to such indications. These indications include acute and recurrent acute pancreatitis, pancreatic exocrine function, sphincter of Oddi dysfunction, and pancreatic neoplasms.

Background and aims: Due to the unavailability of biologic porcine secretin (BPS), 2 synthetic forms of secretin were developed. Our aim is to determine the bioequivalency of the 3 forms of secretin in pancreatic function testing. Methods: In a randomized, crossover design, synthetic porcine (SPS) and synthetic human secretin (SHS) were compared in a group of 12 subjects with chronic pancreatitis undergoing secretin stimulation test (SST). The 2 synthetic forms of secretin were then compared with BPS in 12 subjects utilizing a similar design. Finally, 18 healthy subjects underwent secretin stimulation testing with SHS. Results: There was excellent correlation of peak bicarbonate measurements in the comparison of SPS to SHS (R = 0.967) as well as in the comparison of all 3 forms of secretin (P = 0.08, ANOVA for correlated samples). In the SST, each of the synthetic forms of secretin were 100% accurate in diagnosing chronic pancreatitis in disease subjects and in excluding chronic pancreatitis in normal controls. The synthetic forms of secretin were associated with fewer side effects when compared with BPS with the exception of transient tachycardia which occurred in up to 19% of subjects. Conclusions: The synthetic porcine and human forms of secretin are equivalent to one another and to biologic porcine secretin and can be used interchangeably in pancreatic function testing.

We have isolated, from canine pancreatic juice, two 14-kDa proteins with secretin-releasing activity that had N-terminal sequence homology with canine pancreatic phospholipase A2 (PLA2). In this study we have obtained evidence that secretin-releasing activity is an intrinsic property of pancreatic PLA2. Porcine pancreatic PLA2 from Sigma or Boehringer Mannheim was fractionated into several peaks by reverse phase high performance liquid chromatography. They were tested for stimulation of secretin release from murine neuroendocrine intestinal tumor cell line STC-1 and secretin cells enriched mucosal cell preparations isolated from rat upper small intestine. Each enzyme preparation was found to contain several components of secretin-releasing activity. Each bioactive fraction was purified to homogeneity by rechromatography and then subjected to mass spectral analysis and assays of PLA2 and secretin-releasing activities. It was found that the fraction with highest enzymatic activity also had the highest secretin-releasing activity and the same Mr as porcine pancreatic PLA2. Moreover, it also had the same N-terminal amino acid sequence (up to 30 residues determined) as that of porcine pancreatic PLA2, suggesting that it was identical to the enzyme. Purified porcine pancreatic PLA2 also stimulated secretin release concentration-dependently from both STC-1 cells and a mucosal cell preparation enriched in secretin-containing endocrine cells isolated from rat duodenum. Abolishment of the enzymatic activity by pretreatment with bromophenacyl bromide did not affect its secretin-releasing activity. The stimulatory effect of purified pancreatic PLA2 on secretin secretion from STC-1 cells was inhibited by an L-type Ca2+ channel blocker, by down-regulation of protein kinase C or by pretreatment of the cell with pertussis toxin. It is concluded that porcine pancreatic PLA2 possesses an intrinsic secretin-releasing activity that was independent of its enzymatic activity. This action is pertussis toxin-sensitive and is in part dependent on Ca2+ influx through the L-type channel and activation of protein kinase C.