Radiopharmaceuticals for acutely damaged myocardium. II: Synthesis and evaluation of [203Hg] hydroxymercurifluoresceins.

Six [203Hg] hydroxymercurifluoresceins were prepared by two methods and compared with [3H] fluorescein, [131I] rose bengal, and [203Hg] mercuric nitrate, in a rat model for myocardial necrosis, to determine their specificities for damaged myocardium (DM). The nonhalogenated [203Hg] hydroxymercurifluorescein had the highest ratios of the series for DM/normal heart (51.5+/-13.5) and DM/blood (22.1+/-8.1). Halide substituents at the 2' or 4' positions of the fluorescein moiety decreased the tissue selectivity, and bis-hydroxymercuration had no significant effect. The six tracers studied had greater absolute uptake and better target-to-nontarget ratios than [3H] fluorescein, [131I] rose bengal, or [203Hg] mercuric nitrate, indicating a cooperative effect between the fluorescein and hydroxymercuri-moieties in the overall sequestration process in damaged tissues.