Urinary protein electrophoresis profile in normal and hypertensive pregnancies

By using of modified urine preparation and a highly sensitive SDS-polyacrylamide gel electrophoresis (SDS-PAGE) we determined the urinary protein profile in 21 healthy males, 25 healthy females, 64 patients with uncomplicated pregnancy and 110 hypertensive pregnant women. The urinary protein patterns were similar in controls and in women with a normal pregnancy. There were no increase in the number of protein bands from the 1st trimester to term, and the electrophoresis pattern did not change in the postpartum period. In both groups, an intensively stained protein band with an apparent molecular weight of 105 kD was detected. The 105 kD band was significantly reduced or completely absent in 91 (83%) out of 110 hypertensive pregnant women. The urinary protein electrophoresis profile correlated significantly with the severity of the disease. The 105 kD band disappeared just before or simultaneously with the onset of clinical symptoms in 18 out of 32 hypertensive pregnant women followed throughout pregnancy. Postpartum the 105 kD in urine reappeared at 2 to 14 days after delivery in 49 of the 53 patients. Using a silver staining and Western blot, the 105 kD band was identified as Tamm-Horsfall protein, which is identical to the immunosuppressive glycoprotein uromodulin. The findings in the SDS-PAGE may reflect a transitory tubular dysfunction in cases of pre-eclampsia, which is usually reversible after delivery. The results of our study support the hypothesis of an immunological basis for this disorder.