Characterization of the urinary albumin degradation pathway in the isolated perfused rat kidney.

This study examines the existence of the urinary albumin degradation pathway and the proposed role of receptor-mediated endocytosis in this process using the isolated perfused rat kidney (IPK) model. Albumin-derived peptides in IPK urine are analyzed in terms of their relative size distribution using radioactivity and absorbance at 214 nm, and their susceptibility to trypsin digestion. The effects of perfusing kidneys with concanamycin A and myristoyl trimethyl ammonium bromide (MTMAB), inhibitors of the receptor-mediated endocytosis regulators vacuolar-type H + ATPase (v-ATPase) and dynamin GTPase, respectively, are examined. Normal IPK urine contains mildly degraded (defined as ∼10–40 kDa; 43.0 ± 8.3%) and heavily degraded (defined as