Physiological variations in the urinary excretion of pyridinium crosslinks of collagen

To further validate measurements of the pyridinium crosslinks of collagen as indices primarily of bone resorption in arthritis and other diseases, the effects of day-to-day and nyctohemeral parallel variations, and of renal impairment have been studied. Day-to-day variations measured over 3 weeks were between 16 and 24% for a group of post-menopausal women. Nyctohemeral variations in crosslink excretion of 10-15% were recorded. Although crosslink excretion relative to creatinine was generally higher in the morning than in the evening, no consistent pattern was observed between healthy male and female volunteers and a group of patients with OA or RA. For patients with impaired renal function, with or without arthritis, there was no correlation between crosslink excretion and either creatinine clearance rates or urinary N-acetyl glucosaminidase activity. These results suggested that there was no direct relationship between renal function, at the glomerular or tubular level, and crosslink excretion.