ARTICLES

Extrasplanchnic effect of sulfobromophthalein (BSP) on plasma estrogen levels in the dog

The effect of the drug sulfobromophthalein (BSP) on plasma estrogens in the dog were studied during intravenous infusions of 3H-labeled estrogens. During [3H]estrone infusion, BSP administration caused a marked increase in arterial plasma levels of the radioactive conjugated estrogens, estrone glucosiduronate, estradiol-17 beta glucosiduronate(s), and estrone sulfate. Levels of the unconjugated estrogens, estrone and estradiol-17 beta, were substantially unaltered. Possible mechanisms were investigated. Splanchnic extraction of the conjugates did not change significantly during BSP administration, and renal excretion rose promptly in proportion to the plasma levels, thus virtually excluding decreased biliary or renal excretion. There was no net discharge of estrogen glucosiduronate radioactivity from adipose tissue or muscle following BSP. During [3H]estrone glucosiduronate infusion, BSP again caused an increase in plasma estrone glucosiduronate, thus excluding increased formation (of this conjugate, at least). BSP caused decreased extraction of estrone glucosiduronate by the hindlimb, indicating that decreased metabolism was the probable cause of the elevated plasma levels. BSP also caused decreased formation of unconjugated estrogens by the lungs, indicating that the decreased metabolism includes decreased hydrolysis of estrogen glucosiduronates.