In vivo and in vitro effects of 17α,20β-dihydroxy-4-pregnene-3-one on testicular androgens in atlantic salmon,Salmo salar, mature parr

✍ Scribed by Antonopoulou, Efthimia; Jakobsson, Staffan; Mayer, Ian; Swanson, Penny; Borg, Bertil

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 81 KB
• Volume: 277
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/(sici)1097-010x(19970101)277:1<66::aid-jez7>3.0.co;2-9

✦ Synopsis

Mature Atlantic salmon (Salmo salar) male parr were implanted in June and August with Silastic capsules filled with the progestin 17α,20β-dihydroxy-4-pregnene-3-one (17,20β-P) or with empty capsules. Experiments were terminated in September, when natural androgen levels are at their highest. Radioimmunoassay (RIA) showed that treatment raised plasma levels of 17,20β-P, whereas the content of gonadotropic hormones (GTH I and II) in the pituitary and plasma levels of the androgens testosterone (T) and 11-ketotestosterone (11-KT) were not influenced.

Testicular fragments from mature salmon parr were incubated with different levels of 17,20β-P in combination with T or 17α-hydroxy-4-pregnene-3-one as precursors. A very high level of 17,20β-P (3,000 ng/ml) suppressed 11-KT production, whereas 3, 30, or 300 ng/ml were without effect. Thus, in these experiments physiological levels of 17,20β-P did not suppress androgen 11-KT production or alter pituitary gonadotropin levels, suggesting that some other mechanism is responsible for the natural decline in androgen levels when 17,20β-P levels rise at spawning.