Studies by conventional and “low denaturing” isoelectric focusing on albumin microheterogeneity under normal conditions and in experimental nephrosis

With the aid of ultrathin‐layer isoelectric focusing, rat serum albumin was studied in a group of 6 normal rats and 4 rats affected by an experimentally induced nephrotic syndrome. In normal rats the albumin was microheterogeneous with p I values ranging from 4.7 to 6.1. In animals with the nephrotic syndrome the albumin was almost homogeneous, consisting only of the isoform with the lowest p I of 4.7. The patterns were altered by performing IEF in low denaturing media in presence of 0.5–2 Murea. Under these conditions two rat serum albumin bands with p I 's close to 6.1 were observed. Urinary albumin was highly microheterogeneous in nephrotic rats (p I 4.7–6.1) and less heterogeneous in the normal group(p I 4.7). Pooled urinary albumin from nephrotic rats was fractionated by preparative IEF in granulated gels in four isoforms (A1–A4) with decreasing p I . Both for serum and urinary albumin the fatty acid content in normal and nephrotic syndrome animals was higher in isoforms with low p I .