MN (III) HEMATOPORPHYRIN - A POTENTIAL MR CONTRAST AGENT

Manganese (III) hematoporphyrin (MnHP), a new and stable complex, was prepared, and its toxicity and magnetic resonance (MR) imaging properties were evaluated. In tests of acute and subacute toxicity, no deaths resulted from bolus intravenous injections of 13 or 19 µmol/kg of MnHP, but there was a 33% mortality when the dose was 38 µmol/kg. Laboratory results were normal in the surviving rats. Ultraviolet- visible spectroscopy of the urine and serum of two rats injected 24 hours previously with 38 µmol/kg MnHP revealed no free HP, suggesting in vivo stability of MnHP. Finally, using a standardized imaging protocol, there was a mean increase of 37% in the liver-to-muscle intensity ratios in four rats injected 24 hours previously with 25 µmol/kg MnHP when compared to paired controls (P<.005). In addition, obvious visual increase in the signal intensity of the liver on T1-weighted images was seen in animals tested with 13 and 19 µmol/kg of MnHP. The results suggest that further evaluation of MnHP as an MR contrast agent for the liver is warranted. © Lippincott-Raven Publishers.