Tamm-Horsfall protein in urine after uninephrectomy/transplantation in kidney donors and their recipients

Tamm-Horsfall protein (THP) is a large glycoprotein with unknown physiological function synthesized in the thick ascending limb of the loop of Henle. Urinary THP has recently been suggested as being suitable for monitoring the functional state of transplanted kidneys. In the present study, the urinary excretion of THP after uninephrectomy and transplantation among relatives was determined in order to study the influence of the acute reduction in renal mass on the excretion of this peptide. Glomerular filtration rate (GFR), estimated by the plasma clearance of Cr-51-EDTA, and the excretion rate of THP were measured 2 days before nephrectomy and 5, 12, 26 and 54 days after nephrectomy/transplantation in 22 healthy Living kidney donors and in 16 of their recipients. In the donors, THP excretion rate of the kidney to remain in the donor was 22.3 mu g/min before and 33.7 mu g/min at 5 days after uninephrectomy (p < 0.01) and remained increased by around 40% throughout the study period. GFR of the remaining kidney rose from 47 ml/min before to 61 ml/min at 5 days after uninephrectomy (p < 0.001). The THP excretion rate/GFR ratio remained unchanged in the donors. In the kidney to be transplanted, THP excretion rate was unchanged before and after transplantation. There was no significant increase in GFR in the recipients, which was significantly lower than GFR of the donors all the time. In matched pairs of kidney donors and recipients, the THP excretion rate/GFR ratio tended to be lower in the recipients but the difference was not significant. The correlation between excretion rate of THP and GFR was significant (r = 0.66; p < 0.01). To conclude, uninephrectomy in healthy man was associated with a marked increase of around 40% in the excretion of THP from the kidney that remained in the donor. In the kidney that was transplanted, the THP excretion rate was unchanged. The THP excretion rate was correlated with GFR. The mechanism underlying this association is unknown as THP does not undergo glomerular filtration.