Basal and stimulated serum immunoreactive trypsin in normal subjects

Fasting serum immunoreactive trypsin (IRT) concentrations were measured in 35 healthy subjects. In 10 of them serum IRT levels were also evaluated after administration of secretin (GIH, 75 CU i.v. over 2 minutes); in 7 after a Lundh meal; in 12 after a standard protein meal (Liebig meat extract, 15 g in 150 ml of water) and in 13 after a glucose (1 g/Kg) oral load. Serum IRT was measured by radioimmunoassay (Trypsik kit, CIS, Sorin-Biomedica, Saluggia, Vercelli, Italy). Fasting serum IRT was 25.8 +/- 9 ng/ml (mean +/- SD). No correlation was found between age and serum IRT levels, nor were any statistical differrences observed in IRT concentration between the two sexes. A standard protein meal, Lundh meal or oral load of glucose did not provoke a significant increase in serum IRT levels. Only rapid i.v. injection of secretin was able to induce a significant rise of IRT over basal levels in healthy subjects. This behaviour is probably due more to an engorgement of the pancreatic ductal system with regurgitation of trypsinogen into the blood steam rather than to a direct effect of secretin on the synthesis and secretion of trypsin or to intestinal reabsorption of this enzyme.