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Limit of detection:
80% B/B0: 1.3 pg/ml
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Sensitivity:
50% B/B0: 5 pg/ml
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While testosterone is the primary androgenic male steroid found in mammals, 11-keto testosterone (11-KT) is a second key androgenic steroid found in fish. It occurs in males together with testosterone in amounts which vary from less than 1 ng/ml to as much as 50-100 ng/ml, depending on the species and the stage of the reproductive cycle. In the sea bass, testosterone concentrations are generally higher than 11-KT, with peak levels found after the spawning season. 11-KT, on the other hand, remains at levels less than 1 ng/ml but rises abruptly to 4-6 ng/ml during spermiation at the height of the spawning season.1 11-KT also shows individual variations in Arctic char, with dominant males having significantly higher 11-KT levels.2
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1
Prat, F., Zanuy, S., Carrillo, M., et al. Seasonal changes in plasma levels of gonadal steroids of sea bass, Dicentrarchus labrax L. Gen Comp Endocrinol 78 361-373 (1990).
2
Elofsson, U.O.E., Mayer, I., Damsgård, B., et al. Intermale competition in sexually mature arctic charr: effects on brain monoamines, endocrine stress responses, sex hormone levels, and behavior. Gen Comp Endocrinol 118 450-460 (2000).
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