Fig. 5.

Antibodies to PTPro cause decrease in albumin reflection coefficient (σ_alb) but not σ_dextran. Volume change (ΔV) of glomeruli incubated with an irrelevant antibody (control, black bars) or a polyclonal antibody to PTPro (open bars) was measured following medium change. In A and B, the change in oncotic pressure (ΔΠ) was 12 mmHg. In C. there was no change in oncotic pressure. A: glomeruli were isolated in isoncotic medium containing 4% BSA, and medium was replaced with one containing 1% BSA. ΔV of glomeruli incubated with antibody to PTPro was significantly lower than control, indicating decreased σ_alb and increased glomerular protein permeability. B: glomeruli were isolated in isoncotic medium containing high molecular weight (HMW) dextran, and medium was replaced with one containing HMW dextran of lower oncotic pressure. There was no significant difference in ΔV between control and experimental glomeruli. This is consistent with unchanged relative capillary volume, compliance, and σ_dextran. C: glomeruli were isolated in isoncotic medium containing 4% BSA, and medium was replaced by isoncotic medium containing HMW dextran. Control glomeruli did not change in volume when 4% BSA medium was replaced by isoncotic medium of HMW dextran, while experimental glomeruli showed significant capillary collapse and volume decrease.