Urinary Hydroxyproline as an Index of Collagen Turnover in Bone

Abstract

HYDROXYPROLINE, a nonessential imino acid, occurs in the body almost exclusively in collagen, where it accounts for 13 per cent of the total amino acids.¹ Man excretes hydroxyproline in the urine in bound and free forms.^{2 , 3} The free state of the imino acid accounts for less than 4 per cent of the total amount excreted. Bound hydroxyproline, presumably in a polypeptide, is released by acid hydrolysis and accounts for nearly all the urinary excretion of hydroxyproline.^{2 , 3} A peptide-containing hydroxyproline has been isolated from human urine.⁴ Guinea pigs with osteolathyrism, a disorder of bone and collagen, excrete increased quantities of hydroxyproline . . .