Imaging of lymph node uptake after intravenous administration of indium-111 metalloporphyrins

Indium-111- (111In) labeled tetra (N,N,N-trimethylanilinium) porphyrin (TTAP), tetra (N-methyl-4-pyridyl)porphyrin (TMPyP), and tetra(4-sulfonatophenyl)porphyrin (T4SPP) were synthesized and lymph node uptake was measured in animals after intravenous administration. In rats [111In] TTAP had maximum lymph node to muscle uptake ratios which averaged 85:1 between 24 and 48 hr postinjection. Total lymph node uptake was nearly 1% at that time. Lymph nodes in rabbits were clearly visualized by gamma scintigraphy at 48 hr after i.v. injection of labeled TTAP. These results suggest that 111In-labeled TTAP may be a prototype for the development of a class radiopharmaceuticals which permits visualization of lymph nodes after i.v. administration.