Sodium cholate, a solubilizing agent for the necrosis avid radioiodinated hypericin in rabbits with acute myocardial...

We determined whether sodium cholate (NaCh) could act as a solubilizing agent for the necrosis avid iodine-123-labeled hypericin ((123)I-Hyp) and investigated biodistribution and targetability of this formulation in rabbits with acute myocardial infarction (AMI).

Solubility of radioiodinated hypericin/hypericin (Hyp) in NaCh solutions was evaluated by microscopy. Hyp with (123)I-sodium iodide was performed using hydrogen peroxide as oxidant in 0.06 M NaCh. Radiochemical yield determination and purification were conducted using high performance liquid chromatography. (123)I-Hyp was solubilized in 0.06 M NaCh containing 1.9 × 10(-4 )M Hyp. The formulation was macroscopically inspected and intravenously injected to five rabbits with AMI. At 24 h, biodistribution was evaluated by tissue gamma counting (TGC) and necrosis targetability was assessed by TGC, autoradiography, fluorescence examination and histology.

Microscopically NaCh at 0.06 M shows the best properties for solubilizing the radioiodinated Hyp/Hyp. (123)I-Hyp in 0.06 M NaCh was achieved in 85% with radiochemical purity of 99% after purification. NaCh-dissolved (123)I-Hyp/Hyp shows no particles. By TGC, animals exhibited higher (p = 0.003) radioactivity accumulation in AMI (0.8 ± 0.2% ID/g) than in normal myocardium (0.05 ± 0.02% ID/g), as confirmed by autoradiography, fluorescence measurement and histology. Among organs, the highest uptake of radioactivity was found in liver (15.7 ± 0.6% ID), large (9.7 ± 1.0% ID) and small (5.9 ± 0.6% ID) intestines.

Necrosis avidity of NaCh-dissolved (123)I-Hyp/Hyp and its hepatobiliary excretion were demonstrated. The suitability of NaCh as solubilizing agent of (123)I-Hyp for hotspot imaging of AMI was proved.