Biliary excretion of cholephilic organic acids in anesthetized, male Swiss-Webster mice was compared to that in male Sprague-Dawley rats. The mouse excreted six of the eight compounds examined at a faster or equal rate than the rat. Indocyanine green, rose bengal, phenol-3,6-dibromsulphthalein disulfonate, and eosine were excreted in mice at a rate 120 to 460% higher than in rats. The excretion rates of bromcresol green and sulfobromophthalein glutathione conjugate were similar in the two species, whereas amaranth was excreted at a slightly lower rate in mice than in rats. Biliary excretion of sulfobromophthalein (BSP), especially its glutathione conjugate, was significantly lower in the mouse which corresponded to a difference in BSP-glutathione transferase activities between the two species (mouse, 0.97; rat, 1.35 μmol/min/g liver). The depression of bile production by cholestatic organic anions was stronger, and the stimulation of bile flow by choleretic acids was weaker in mice than in rats. Differences in biliary bile acid excretion (mouse, 3.62; rat, 1.42 μmol/kg/min), bile flow (mouse, 102; rat, 69 μl/kg/min), and liver weight (mouse, 57; rat, 38 g/kg) but not hepatic ligandin concentration (mouse, 132; rat, 214 nmol BSP/g liver) may explain the variations in the biliary organic anion excretion between mice and rats.
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