Determination of human pancreatic cationic trypsinogen in serum by radioimmunoassay

Unraveling the complex genetic model for cystic fibrosis: pleiotropic effects of modifier genes on early cystic fibrosis-related morbidities

The existence of pleiotropy in disorders with multi-organ involvement can suggest therapeutic targets that could ameliorate overall disease severity. Here we assessed pleiotropy of modifier genes in cystic fibrosis (CF). CF, caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, affects the lungs, liver, pancreas and intestines. However, modifier genes contribute to variable disease severity across affected organs, even in individuals with the same CFTR genotype. We sought to determine whether SLC26A9, SLC9A3 and SLC6A14, that contribute to meconium ileus in CF, are pleiotropic for other early-affecting CF co-morbidities. In the Canadian CF population, we assessed evidence for pleiotropic effects on (1) pediatric lung disease severity (n = 815), (2) age at first acquisition of Pseudomonas aeruginosa (P. aeruginosa) (n = 730), and (3) prenatal pancreatic damage measured by immunoreactive trypsinogen (n = 126). A multiple-phenotype analytic strategy assessed evidence for pleiotropy in the presence of phenotypic correlation. We required the same alleles to be associated with detrimental effects. SLC26A9 was pleiotropic for meconium ileus and pancreatic damage (p = 0.002 at rs7512462), SLC9A3 for meconium ileus and lung disease (p = 1.5 × 10(-6) at rs17563161), and SLC6A14 for meconium ileus and both lung disease and age at first P. aeruginosa infection (p = 0.0002 and p = 0.006 at rs3788766, respectively). The meconium ileus risk alleles in SLC26A9, SLC9A3 and SLC6A14 are pleiotropic, increasing risk for other early CF co-morbidities. Furthermore, co-morbidities affecting the same organ tended to associate with the same genes. The existence of pleiotropy within this single disorder suggests that complementary therapeutic strategies to augment solute transport will benefit multiple CF-associated tissues.

Sphincter of Oddi function studied by radioimmunoassay of biliary trypsin in patients with bile duct stones and in controls

The trypsin level in bile was studied by radioimmunoassay in a prospective series of 63 patients with gallstone disease but without signs or symptoms of cholecystitis or pancreatitis in order to find indirect evidence of a retrograde flow of pancreatic juice. Mobile duct stones were present in 18 patients and impacted stones in 12. The remaining 33 patients had stones only in the gallbladder and served as controls. The average intraoperative trypsin level of the ductal bile was normal, both in the control group and in the group with stones occluding a potential retrograde reflux of pancreatic juice. After removal of the impacted stones, the bile showed a significantly higher trypsin level. The average intraoperative trypsin level for the group with mobile stones was significantly higher than that of the control group, and was further increased 10 days postoperatively. The trypsin level of ductal bile from 23 of the 30 patients (77%) with bile duct stones exceeded that of the 33 patients with stone-free bile ducts, indicating an inflow of pancreatic juice to the bile ducts of patients with bile duct stones. The present results correspond well to those in a previous report on retrograde phasic contractions of the sphincter of Oddi in the majority of patients with bile duct stones. This dysfunction of the sphincter, which persisted for 10 days after surgical stone removal, may be the primary disorder, probably consisting of a retrograde propulsive activity of the sphincter of Oddi.

Assay of serum immunoreactive trypsin in dried blood spots and the early detection of cystic fibrosis

Immunoreactive trypsin (IRT) content in blood spots from 17 cystic fibrosis (CF) children born between 1975-80 were assayed with reagents from two commercial radioimmunoassay kits. The manufacturers' procedures were modified to allow assay of blood spot IRT. Half of the CF samples had a significantly raised IRT content compared to normal blood spots. Of the blood spots from five children whose meconium screening gave negative results, three or five (depending on the kit used) had a raised IRT content. On the other hand, less than 50% of children initially detected by meconium screening had raised blood spot IRT values. In our hands, analysis of blood spots for IRT does not consistently identify the newborn with CF and offers no advantage over other screening methods.