EXPERIMENTAL EVALUATION OF THE VASCULAR EFFECTS AND TRANSPORT OF AN IODINATED MACROMOLECULAR CONTRAST-MEDIUM

RATIONALE AND OBJECTIVES. For assessment of the tissue blood pool and overall vascularity, macromolecular contrast media have significant ad vantages over low molecular weight contrast agents, The authors evalua ted the vascular effect and transport of a new macromolecular contrast media (MMCM), an iodinated dextran polymer of 32 kDa, METHODS. The ne w MMCM was obtained from dextran activated by carboxy methylation, fol lowed by linkage with triiodinated aminophtalamid conjugates, To detec t whether the tracer induces vascular leakage, MMCM (350 mg I/kg) was administered intravenously in 10 mice, or applied on the cremaster mus cle of 26 mice previously injected with carbon particles; after 30 or 45 minutes, the cremaster was fixed and examined by optical microscopy . For investigation of the vascular transport 3, 5, and 15 minutes aft er MMCM administration, various tissue fragments were processed and ex amined by electron microscopy. RESULTS. In all vascular beds examined, MMCM does not induce plasma extravasation and the probe was detected mostly within the vascular lumen, At the ultrastructural level, a smal l fraction of MMCM was found in endothelial plasmalemmal vesicles (end osome-like structures) and, in time, transcytosed to the subendothelia l space, No intercellular junctions were permeated by MMCM. CONCLUSION S. The MMCM induces no vascular leakage and it is retained mainly in t he plasma, Transport of MMCM is restricted to endothelial vesicles, wh ich may explain, in part, its prolonged vascular space retention.