Pharmaceutical properties, biodistribution, and imaging characteristics of manganese-mesoporphyrin. A potential hepatobiliary contrast agent for magnetic resonance imaging.

Abstract

Manganese (III) mesoporphyrin (Mn-mesoporphyrin) was investigated for its pharmaceutical properties and magnetic resonance imaging characteristics as a potential hepatobiliary contrast agent. Solubility, partition coefficient, plasma binding, proton relaxation enhancement, biodistribution, biliary excretion, liver extraction ratio, and liver enhancement were measured in various in-vitro and in-vivo systems. Mn-mesoporphyrin was soluble and stable at moderate alkaline pH in phosphate buffer. The octanol/water coefficient was 25.98, and the compound was highly protein bound. R1 for water and plasma were 1.94 and 2.35 L/mmol sec, respectively. R1 in liver was calculated to be 15.72 L/mmol sec. Biodistribution studies in rats and mice confirmed hepatotrophic properties and biliary excretion was 65% over 24 hours. First pass liver uptake was 15%. Magnetic resonance imaging studies showed persistent liver enhancement at 0.05 mmol/kg. Mn-mesoporphyrin is a lipophilic compound that shows potential as a hepatobiliary magnetic resonance contrast agent.