TISSUE DISTRIBUTION AND EXCRETION OF TC-99M-DISOFENIN IN 3 MARINE SPECIES - PLEURONECTES-AMERICANUS (WINTER FLOUNDER), HOMARUS-AMERICANUS (LOBSTER), AND MYA-ARENARIA (SOFT-SHELL CLAM)

To determine the pharmacokinetics of a small lipophilic molecule in vi vo, the distribution and accumulation of Tc-99m-radiolabelled disofeni n (diisopropylacetanilide iminodiacetic acid) were traced during 19911 992 by scintigraphy and gamma well counting in winter flounder (Pleuro nectes americanus collected from Boston Harbor and Long Island Sound i n 1992), lobsters (Homarus americanus collected from Massachusetts Bay in 1991), and soft-shell clams (Mya arenaria purchased in 1991). The agent was distributed throughout the bodies of lobsters within 12 s, t hroughout flounder within 40 s, and throughout clams within 2 min. It was concentrated most strongly by the liver of flounder, which contain ed 61.2 +/- 7.8 % of the injected dose within 1 h of injection, and by the lobster hepatopancreas. Accumulation also occurred in the flounde r kidney, lobster antennal glands, and the kidney and pericardial glan ds of clams. The compound was rapidly excreted from the flounder liver into the gall bladder, and from the lobster hepatopancreas into the s tomach. The data suggest its excretion from the lobster antennal gland s and clam kidneys. The rate of clearance of disofenin from the body v aried among species: 99 +/- 2.1 % of the initial dose remained in flou nder sampled 16 to 24 h after injection, compared to 80.5 +/- 7 % rema ining in the lobster after 15 h, and 87.4 +/- 5.9 % remaining in clams after 27 h. The clearance rates in flounder and lobster are considere d to be minimum values because of the lack of gut activity in unfed in dividuals. Overall, these in vivo tracer studies establish the utility of scintigraphy for assessing the uptake and excretion of a lipid sol uble compound in different taxa, and may be applicable for evaluating disease and/or environmental effects on organ function in marine anima ls.