Abstract
The influence of modeled femur callosity on the biodistribution of 188Re-labeled pentaphosphonic acid (188Re-PPA) in rats was studied. The radiopharmaceutical was injected into a tail vein 14 d after fracture. It was established that the presence of bone callosity had a significant influence on 188Re-PPAbiodistribution in soft tissues and organs. 188Re-PPA showed good stability in vivo because its uptake by thyroid gland was low compared to that of unbound 188Re. The maximum activity levels were observed in bone callosity (up to 1%/g), bone tissue in general, liver, and kidneys. The 188Re-PPAconcentration in bone tissue of rats with bone callosity was 2.4 – 10.6 times lower than that in bone tissue of intact animals. The maximum 188Re-PPAactivity in bone tissue of intact rats and those with bone callosity 1 h after i.v. injection was 2.12 and 0.42%/g, respectively. The coefficients of differential accumulation (CDA) of drug activity in bone callosity relative to soft tissues and organs were calculated. 188Re-PPAuptake by bone lesion was greater than that by normal bone tissue. The CDA values enabled the accumulation dynamics and elimination rate of 188Re-PPA from soft tissues and organs to be compared with those from bone fracture. In addition, the CDA values allowed the optimum period for carrying out skeletal scintigraphic studies using a gamma camera to be determined. In conclusion, 188Re-PPA had appropriate biological characteristics for use as a bone-pain pallation agent for the treatment of bone metastases.
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