Detection of colipase in serum and urine of pancreatitis patients.

Colipase, like other pancreatic proteins, is liberated into the circulation in acute pancreatitis. Its concentration was measured in serum by a turbidimetric and in urine by a titrimetric method. The principle of both assays is based on the reactivation of bile acid inhibited, pure human pancreatic lipase by colipase. Whereas in healthy individuals colipase was found neither in serum nor urine (detection limit approximately 6.5 micrograms/1), a wide concentration range was observed in 29 patients with acute pancreatitis. Urine values varied between 3.8 and 7121 micrograms colipase/g creatinine; in serum levels up to 664 micrograms/1 were found. There was no correlation with serum lipase activity: On a molar basis, the ratio of serum colipase to serum lipase ranged between less than 0.04 and 2.14, but was below 1 in most sera. Colipase is rapidly removed from the circulation by glomerular filtration, its elimination rate from serum being more than twice as fast as that of lipase. This results in a constant decrease of the colipase/lipase ratio during the course of the disease. Probably determination of colipase is of no direct diagnostic value in pancreatic disorders, but our findings are of considerable significance for the measurement of serum lipase in the presence of bile acids, particularly with regard to turbidimetric assays. We conclude that lipase activity values obtained by these methods are mainly dependent on the degree of saturation of the enzyme with its cofactor and not on the true lipase concentration.