Collagen metabolism of rats in various hormonal and dietary conditions

¹ Department of Physiological Chemistry, University of Minnesota Medical School, Minneapolis, Minnesota

Injections of glycine-2-C¹⁴ into male rats were followed by determination of specific activity of femur and tail tendon collagen glycine and free plasma glycine. Hydroxyproline contents of bones were used to calculate total collagen glycine radioactivities. Although part of the femur collagen was relatively metabolically stable, a slow replacement appeared to take place. Specific activities of tail tendon collagen glycine, in contrast to femur collagen glycine, increased from 3 to 7 days after isotope administration. This difference appeared to be related to specific activities of free plasma glycine. Animals on an inadequate diet presented a different pattern of isotope content than animals on a complete diet. Results with hypophysectomized animals indicated turnover of femur collagen. Hypophysectomy resulted in a differential effect on femur and tail tendon collagen. Parathyroid-extract treatment increased the total collagen content of femurs. During certain experimental periods, specific activities of femur and tail tendon collagen glycine of parathyroid-treated animals approached the specific activity of free plasma glycine more rapidly than normal animals.