DIFFERENTIAL EXPRESSION OF URINARY INTER-ALPHA-TRYPSIN INHIBITOR TRIMERS AND DIMERS IN NORMAL COMPARED TO ACTIVE CALCIUM-OXALATE STONE FORMING MEN

Purpose: We determine if the immunoreactive profile of urinary inter-a lpha-trypsin inhibitor can be used to distinguish between normal indiv iduals and individuals with calcium oxalate stone disease. Materials a nd Methods: Urinary proteins were dialyzed against water (15 kDa. mole cular weight cutoff), lyophilized and resolved by sodium dodecyl sulfa te-polyacrylamide gel electrophoresis (6% acrylamide, reducing conditi ons) followed by Western blot. Inter-alpha-trypsin immunoreactive prot eins were detected by enhanced chemiluminescence. Stone formation was confirmed to be active radiologically or passed as stone or gravel wit hin 12 months of the sample, Stone composition was confirmed crystallo graphically. Normal individuals had no personal or familial history of urolithiasis and matched stone forming patients regarding race (white ) and age (23 to 71 years old). Urine from a total of 101 individuals was analyzed. Results: The intact inter-alpha-trypsin trimer (similar to 220 to 240 kDa,) and heavy chain (HC) 2-bikunin/HCl-bikunin dimers (similar to 115 to 130 kDa,) were detected more often in stone forming men (23 of 26 [89%] and 26 of 26 [100%], respectively) than in normal individuals (6 of 26 [23%] and 5 of 26 [19%], respectively, p < 0.000 1). In those normal individuals who expressed inter-alpha-trypsin trim er and HC-bikunins the relative intensities were 5.3 +/- 1.4% and 16.3 +/- 17.1% of the stone forming controls, respectively. The identity o f high molecular weight-inter-alpha-trypsin immunoreactive bands was c onfirmed using antibodies against the individual subunits (HC1, HC2, H C3, bikunin). In contrast to men high molecular weight-inter-alpha-try psin's were readily detected in normal and stone forming women with eq ual frequency (inter-alpha-trypsin-trimer p = 0.1337, HC-bikunins p = 0.2836): inter-alpha-trypsin-trimer 17 of 18 [94%] and 9 of 13 [77%]; HC-bikunins 17 of 18 [94%] and 10 of 13 [85%]). Inter-alpha-trypsin-tr imer and HC-bikunins, respectively, were detected in 2 and 5 of 10 pat ients with chronic renal disease. Expression was not related to hematu ria or proteinuria. Conclusions: Immunoreactive profiles of urinary pr oteins may be able to be developed into a useful diagnostic tool to id entify active stone formation, although a separate panel may be requir ed for men and women. It is possible that these differences may provid e clues as to why the incidence of stone disease is higher in men than women.