Limit of detection: 80% B/B₀: 1.3 pg/ml · Sensitivity: 50% B/B₀: 5 pg/ml · 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

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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Pradelles, P., Grassi, J., Maclouf, J.A. Enzyme immunoassays of eicosanoids using acetylcholinesterase as label: An alternative to radioimmunoassay. Anal Chem 57 1170-1173 (1985).

Maclouf, J., Grassi, J., Pradelles, P. Development of enzyme-immunoassay techniques for the measurement of eicosanoids. (1987).

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).

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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