Figure 4.

Mathematic model of albumin uptake along the PT. (A) Albumin-to-creatinine ratio (blue curve) and LMWP-to-creatinine ratio (red curve) along the human PT were modeled as described in the Methods. The models were fitted to the measured fractional reabsorbance in humans (0.986 for albumin and 0.9997 for LMWP) at the end of the tubule. In patients with LS, the estimated fractional reabsorptions for albumin and LMWP are 0.86 and 0.70, respectively. As denoted by the black arrows, an approximately 30% reduction in PT length is predicted to result in the tubular proteinuria phenotype characteristic of LS. The effects of reduced SNGFR on urinary excretion profiles of albumin (B) and LMWP (C) are plotted. A progressively greater reduction in PT length would be needed to produce the predicted urinary excretion profile as SNGFR declines from 100% to 60% of control.