Plasma kinetics of ingested tritiated estradiol and the influence on estradiol plasma levels in the cultured Siberian sturgeonAcipenser baeri.

Plasma kinetics of tritiated estradiol (E2) were studied in the Siberian sturgeonAcipenser baeri in order to explain the large amount of E2 found in plasma of 4, 5 and 10-year-old cultured males. This work presents two approaches. The first is based on a single ingestion of(3)H-labelled E2, which allowed us to plot model curves of resorption and elimination processes. The second deals with chronic ingestion of(3)H-labelled E2 during a five day period, twice a day, based on a rhythm copied from the feeding practice on a fish farm. Three different doses were tested, based on the amount present in fish diets. Oral administration of E2 to sturgeon leads to E2 accumulation and a saturation of the metabolic processes generally involved in the elimination of aromatic xenobiotics. An explanation of this progressive accumulation of E2 in sturgeon plasma has to take into account the steroid binding proteins. Their synthesis could be induced by the orally administrated E2 and protect it from metabolism.