The retention in bone of ¹²⁵I-labeled heparin over time. Rats were injected with ¹²⁵I-labeled heparin (□) or ¹²⁵I-labeled BSA (▵) over a 28-day period. At various intervals over the 28 days of heparin treatment and for an additional 56 days thereafter, four rats from each group were killed, their femurs isolated. The amount of heparin that had accumulated in each femur was then determined by use of a γ-counter. Counts were corrected over time for the decay of ¹²⁵iodine and converted to ng of heparin or BSA/g tissue. Data are expressed as mean ± SEM.