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).

Maxey, K.M., Maddipati, K.R., and Birkmeier, J. Interference in enzyme immunoassays. J Clin Immunoassay 15 116-120 (1992).

Pradelles, P., Grassi, J., and 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., and Pradelles, P. Development of enzyme-immunoassay techniques for the measurement of eicosanoids. 355-364 (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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