anesthesia [1 mL.kg21 i.p. ketamine (Imalgene 500, Merial) and 0.5 mL.kg21 i.p. xylazine (Rompun, Bayer)] and positive pressure ventilation, as described [30]. This protocol was performed under a permit from the French Veterinary Services Directorate. Two types of control animals were used: healthy rats, and healthy rats which had undergone a simple throracotomy (sham- operated). 99mTc-biotin-collagelin blood kinetics and biodistribu- tion were investigated by counting blood samples (taken from a jugular catheter) for 6 h after i.v. injection, and organs (extracted after sacrifice) 2 h after injection in a gamma-counter, together with aliquots of the injected preparation (CobraII, Packard, Meriden, USA). Ex vivo myocardial labeling and isotopic imaging were performed 4 weeks after the coronary ligature (or throracotomy), when the lesions had had the time to heal. Rat aorta and rat myocardial scar sections were incubated in the presence of 99mTc-biotin-collagelin, +/29012 moAb, or 99mTc-biotin-control peptide Pc (120 MBq/ml of RPMI) for 2 h. The tissues were then rinsed 5 times for periods of 1 minute, and exposed to the gamma-camera as well as to the instant imager for quantitative autoradiography (Instant Imager, Packard) for 15 h. For in vivo experiments, radiotracers (70 MBq) were adminis- tered i.v. to anesthetized animals (pentobarbital i.p. 6 mg/100 g BW, Ceva Sante´ Animale, France) within 2 h of radiolabeling. Scintigraphic images were obtained 0–2 h, 4 h, 6 h, 10 h and 24 h after injecting 99mTc-streptavidin-biotin peptides and 0–3 h after injecting 99mTc-biotinylated peptides. Planar and tomo- graphic 1-h acquisitions were performed using a dedicated small animal cIMAGER system (Biospace Lab, Paris, France) equipped with 2 parallel low-energy high-resolution collimators (matrix 1286128, 15% energy window centered on 140 KeV). Tracer uptake in the left cardiac area was assessed visually. Two regions of interest were drawn on the scintigrams, over the heart and over the right lung. The mean activity (cpm) per pixel was determined in each region of interest. Then heart-to-lung activity ratios (HLR) were calculated on both planar and transversal tomographic images. After sacrificing the animals, the heart was removed and frozen, then 20-micrometer thick myocardial sections were cut perpen- dicular to the short axis of the ventricles in a cryostat, and exposed in a radioimager for 16 h. According to calibration studies References 1. Murray CJ, Lopez AD (1997) Alternative projections of mortality and disability by cause 1990–2020: Global Burden of Disease Study. Lancet 349: 1498– 1504. 2. de Ledinghen V, Le Bail B, Rebouissoux L, Fournier C, Foucher J, et al. 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The myocardial sections used for autoradiography, and contiguous heart sections (5 mm) fixed in acetone (220uC), were stained with hematoxylin-eosin, Masson’s trichrome and picrosirius red to determine the location and extent of the fibrotic myocardial scarring. The lung fibrosis model was realized as already described [32]. Male C57BL/6J mice, aged 6–7 weeks were kept in accordance with INSERM rules. On day 0, mice were administered 80 mg of bleomycin hydrochloride (Bleomycine Bellon, Aventis, France) intratracheally. Mortality was assessed daily over a 14 day period. Na¨ıve mice were used as controls. At day 14 mice received one intravenous injection of 99mTc- B- collagelin or of 99mTc- B-Pc (3 MBq). Then planar whole-body scintigraphic imaging (60 min duration) was performed 1 hour after tracer injection as above. At the end of the experiment, animals were sacrificed and lung were dissected for gamma counting, autoradiography, and histology. Statistical analysis Scintigraphic and autoradiographic quantitative parameters are expressed as means6SEM. The unpaired t-test was used to compare collagelin data in 2 groups of animals (rats with myocardial scar versus sham-operated rats), or radiotracers in the rats with a myocardial scar (collagelin versus control peptide Pc). The level of significance was set at p,0.05. Acknowledgments We thank Dr. Jean-Michel Camadro (Jacques Monod Institute, University Paris 6 and 7, Paris, France) for his help in carrying out and interpreting the SPR analysis, Dr Mary Osborne-Pellegrin and Miche`le Coutard for helpful discussion. Author Contributions Conceived and designed the experiments: LSM DLG PB MJP. Performed the experiments: JM SL AM LL FH JMS JBM. Analyzed the data: JM LSM PB MJP. Contributed reagents/materials/analysis tools: JM LSM SL LL CBM JBM PB MJP. Wrote the paper: LSM PB MJP. 10. 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