Technetium-labeled heparin kinetics studies were undertaken in 12 hemodialyzed patients, where heparin was used over a long term (1 to 10 years) for anticoagulation of the extracorporeal circuit. The 99mTc-heparin (99mTc VECTOSCINT, Solabco Nuclear, Coutras, France) used has a 10 mCi activity and a labeling efficiency of more than 95%. Two healthy subjects served as control. After an i.v. bolus of 2 ml 99mTc-heparin, corresponding to 170 +/- 10 IU, radioactivity of kidney, liver, knee and shoulder was recorded with a gamma camera at t1-h, t3-h and t6-h during 120, 152 and 215 s, respectively. Radioactivity recorded was computerized, giving quantitative data for comparison. In hemodialyzed patients, accumulation of radioactivity (mean +/- SEM 10(6) x activity count) was significantly higher at the knee (11.3 +/- 1.1 vs. 4.9 +/- 0.4; p < 0.05; 13.4 +/- 1.1 vs. 5.7 +/- 0.7; < 0.02; and 14.7 +/- 0.8 vs. 5.3 +/- 0.6; < 0.001), and on the shoulder (17.3 +/- 1.1 vs. 10.7 +/- 1.4; p < 0.05; 19.9 +/- 1.0 vs. 10.9 +/- 1.7; < 0.01; 20.8 +/- 1.1 vs. 10.1 +/- 0.9; < 0.01) at t1-h, t3-h and t6-h, respectively, than in control subjects at the same areas. Although direct evidence is not in hand, accumulation of heparin in bone tissue due to renal excretion failure could play a role in mineral metabolism resulting in osteopenia in hemodialyzed patients.