- Last Update On : 2013-01-28
Urine protein is a mixture of plasma proteins, renal tubular proteins and those from the lower urinary tract. Very little plasma protein crosses the glomerular capillary membranes in healthy individuals. Traces of albumin and beta globulins may be filtered, but are largely reabsorbed by the proximal tubule cells. Cells of the ascending Loop of Henle may secrete Tamm-Horsfall mucoprotein.
Abnormally increased quantities of protein may appear in the urine as a consequence of three major mechanisms.
- Glomerular disease is the most common cause of proteinuria.
- Less commonly, low -molecular weight plasma proteins may spill over into the urine when they are present in high concentrations. Examples include Bence Jones proteins in multiple myeloma, myoglobin in rhabdomyolysis, and hemoglobin in intravascular hemolysis.
- The third mechanism of proteinuria is impaired renal tubular reabsorption of proteins in tubulointerstitial kidney diseases. <