A cause of discrepancy between values for urinary protein as assayed by the Coomassie Brilliant Blue G-250 method and the sulfosalicylic acid method.

In simultaneous assays of urinary proteins by the Coomassie Brilliant Blue G-250 (CBB) and the sulfosalicylic acid (SSA) methods, we noticed that about 18% of samples showed about twice higher protein values by the former method than by the latter. Some urinary proteins are soluble in SSA and react with CBB. Examinations with sodium dodecyl sulfate/polyacrylamide gel electrophoresis showed that these proteins migrated in 13 protein bands having relative molecular masses ranging from 15 000 to 230 000. The protein corresponding to the most intensely stained band in urine samples from the patients studied (with malignant tumors, renal disorders, etc.) had an Mr of 45 000; that in the pattern for healthy subjects had an Mr of 94 000. The former was identified as alpha 1-acid glycoprotein, the latter as Tamm-Horsfall mucoprotein.