Renal tubular transport of hydroxyproline peptides: evidence for reabsorption and secretion.

Abstract

Hydroxyproline peptide and insulin renal plasma clearances were examined in 4 normal males under basal and loading conditions. In addition, endogenous peptide clearance studies were conducted in 33 subjects with a spectrum of diseases of the kidney and endocrine systems. Transport of hydroxyproline peptide in the normal, basal state kidney was shown to involve glomerular filtration and net tubular reabsorption, but if the plasma peptide load to the tubules was increased, net tubular secretion was demonstrated. In patients with glomerular and/or tubular disease, no alteration in renal peptide excretion was found. In patients with endocrine disorders, the most unusual observation was the demonstration of hydroxyprolien peptide tubular secretion in hyperthyroidism. The significance of these results in terms of collagen metabolism is discussed. Hydroxyproline peptide and insulin renal plasma clearances were examined in 4 normal males under basal and loading conditions. In addition, endogenous peptide clearance studies were conducted in 33 subjects with a spectrum of diseases of the kidney and endocrine systems. Transport of hydroxyproline peptide in the normal, basal state kidney was shown to involve glomerular filtration and net tubular reabsorption, but if the plasma peptide load to the tubules was increased, net tubular secretion was demonstrated. In patients with glomerular and/or tubular disease, no alteration in renal peptide excretion was found. In patients with endocrine disorders, the most unusual observation was the demonstration of hydroxyprolien peptide tubular secretion in hyperthyroidism. The significance of these results in terms of collagen metabolism is discussed.