Glomerular charge selectivity in primary glomerulopathies.

1. Glomerular charge selectivity was assessed using the ratio of the clearance of pancreatic isoamylase to the clearance of the more anionic salivary isoamylase ( C PAm / C SAm ) in 53 patients with primary glomerulopathies (minimal change nephropathy, idiopathic membranous nephropathy, IgA nephropathy) and a wide range of albumin excretion rates and in 31 healthy subjects. Fractional clearances of pancreatic and salivary isoamylases (FC PAm , FC SAm ) and of albumin (FC Alb ) were also measured. 2. C PAm / C SAm and FC PAm were negatively correlated with FC Alb for the whole patient group ( r s = −0.56 and r s = −0.65, respectively, P SAm with FC Alb . 3. For patients with near-normal albumin excretion rates ( C PAm / C SAm between the three types of glomerulopathy or between patients and healthy subjects. 4. These data suggest that glomerular charge selectivity at the size of amylase (which is smaller than albumin) is progressively lost as albuminuria increases from normal to the nephrotic range. Size restriction progressively increases until albuminuria is very heavy. When the albumin excretion rate is near normal, charge selectivity is also normal in the three main forms of primary glomerulopathy.