UNLABELLED: Exogenous albumin peptides influence the processing of albumin during renal passage. BACKGROUND/AIMS: This study investigates the hypothesis that there will be peptide regions in albumin that will effectively compete for the receptors associated with the renal processing of albumin. METHODS: We employ albumin peptides prepared from albumin by trypsin digestion. The presentation of the exogenous peptides along with intact [(3)H]albumin to the kidney was made by intravenous injection into rats. The excretion rate and integrity of urinary [(3)H]albumin was measured. Similar experiments were performed with the use of gelatin peptides produced by trypsin digestion as controls. The formation of [(3)H]albumin derived fragments by extrarenal sources was also examined in rats with nonfiltering kidneys. RESULTS: In the presence of exogenous albumin-derived peptides there was a significant increase in the proportion of larger [(3)H]albumin fragments in the urine. This is a reversible effect. There was no significant change when gelatin peptides were used. The albumin peptides also increase the fractional clearance of [(3)H]albumin. There were no [(3)H]albumin-derived fragments produced in plasma over a 4-hour circulation period in rats with nonfiltering kidneys. CONCLUSIONS: This study demonstrates that albumin fragments, which are produced by the kidney and not by extrarenal sources, are exclusively excreted in the urine. Exogenous albumin peptides were able to specifically exert a competitive effect on the renal enzyme cleavage of intact albumin. Copyright 2002 S. Karger AG, Basel
UNLABELLED: Exogenous albumin peptides influence the processing of albumin during renal passage. BACKGROUND/AIMS: This study investigates the hypothesis that there will be peptide regions in albumin that will effectively compete for the receptors associated with the renal processing of albumin. METHODS: We employ albumin peptides prepared from albumin by trypsin digestion. The presentation of the exogenous peptides along with intact [(3)H]albumin to the kidney was made by intravenous injection into rats. The excretion rate and integrity of urinary [(3)H]albumin was measured. Similar experiments were performed with the use of gelatin peptides produced by trypsin digestion as controls. The formation of [(3)H]albumin derived fragments by extrarenal sources was also examined in rats with nonfiltering kidneys. RESULTS: In the presence of exogenous albumin-derived peptides there was a significant increase in the proportion of larger [(3)H]albumin fragments in the urine. This is a reversible effect. There was no significant change when gelatin peptides were used. The albumin peptides also increase the fractional clearance of [(3)H]albumin. There were no [(3)H]albumin-derived fragments produced in plasma over a 4-hour circulation period in rats with nonfiltering kidneys. CONCLUSIONS: This study demonstrates that albumin fragments, which are produced by the kidney and not by extrarenal sources, are exclusively excreted in the urine. Exogenous albumin peptides were able to specifically exert a competitive effect on the renal enzyme cleavage of intact albumin. Copyright 2002 S. Karger AG, Basel