OCCURRENCE AND IN-VITRO BIOSYNTHESIS OF 11-KETOTESTOSTERONE IN SIBERIAN STURGEON, ACIPENSER BAERI BRANDT MATURING FEMALES

High levels of 11-ketotestosterone (11KT) were found (49 to 160 ng ml( -1)) in plasma of Siberian sturgeon females during the end of their re productive cycle. These levels were measured either by specific radioi mmunoassay, or both by specific radioimmunoassay and by UV absorption after HPLC (isocratic conditions, 33% methanol, 26% acetonitrile, 41% water). In order to find the origin of 11KT synthesis, ovaries were in cubated (30 min and 2h at 20 degrees C) with tritiated 17-hydroxyproge sterone (17OHP) or with tritiated androstenedione (A4). Testosterone ( conversion rate from tritiated 17OHP: 4%) and 11-ketotestosterone (con version rate from tritiated A4: 1.6%) were identified as metabolites o f respectively 17OHP and A4 (TLC, HPLC and crystallization). 11 beta-h ydroxyandrostenedione (11 beta OHA4) and 11 beta-hydroxytestosterone ( 11 beta OHT) were suggested to be intermediate metabolites. Besides in terrenal and blood cells were incubated respectively with tritiated co rtisol and tritiated A4. 11 beta OHA4 was identified in interrenal inc ubation (yield from tritiated cortisol: 1.2%). 11KT in interrenal (yie ld from tritiated cortisol: 0.14%), and 11 beta OHA4 and 11KT in blood cells (yield from tritiated A4: 1.6%), were suspected to be synthesiz ed (TLC, HPLC, acetylation). No significant metabolization of tritiate d cortisol could be found in liver. The possible contribution of each of these tissues to high 11KT levels found in plasma is discussed.