Urinary markers of type I collagen degradation in the dog

Urinary assays for type I collagen metabolites provide a non invasive index of bone resorption in humans, and are widely used in the management of pat ients with metabolic bone diseases. The specific aims of this study were to investigate the feasibility of using commercial human assay kits for quant ifying the urinary excretion of type I collagen metabolites in dogs of diff erent ages. Urine and serum samples were collected from 35 beagle dogs in f ive age groups (0 to 1 years, 1 to 2 years; 2 to 3 years; 3 to 7 years; > 8 years old). Urinary concentrations of pyridinoline (Pyd), deoxypyridinolin e (Dpd), and the carboxy- and amino-terminal crosslinked telopeptides of ty pe I collagen (CTx and NTx, respectively) were measured with commercial enz yme-linked immunoassay kits. Serum concentrations of another type I collage n metabolite, the carboxy-terminal cross-linked teloptide of type I collage n (ICTP), were measured with a commercial radioimmunoassay. Dilutional studies indicated that the four urinary assays show specific cro ss-reactivity with canine urine. Age-related differences in urinary marker excretion were identified, with young dogs excreting the highest concentrat ions of Pyd, Dpd, NTx and CTx. The correlation between the individual urina ry markers was excellent (r = 0.87 to 0.98), while the correlation between serum ICTP and individual urinary markers was weaker (r = 0.52 to 0.64). Th ese results validate the usefulness of the commercial assay kits in monitor ing type I collagen metabolism in dogs. Histomorphometric studies have conf irmed the relationship between collagen degradation and bone resorption in humans, and similar studies are now needed in dogs. (C) 2000 Harcourt Publi shers Ltd.