Circadian changes in serum concentrations of steroids in Japanese char Salvelinus leucomaenis at the stage of final maturation.
Circadian changes in serum concentrations of testosterone (T), 11-ketotestosterone (11KT), estradiol-17beta (E2), 17alpha,20beta-dihydroxy-4-pregnen-3-one (DHP), 17alpha-hydroxyprogesterone (OHP), cortisol (F) and progesterone (P) were investigated in the spermiated/ovulated Japanese char Salvelinus leucomaenis for over three days using newly developed time-resolved fluoroimmunoassays. Testosterone and DHP in both sex and 11KT in male showed significantly (P<0.05) higher serum levels just before/after onset of darkness (15:00 or 18:00), and the levels during night and daytime were significantly (P<0.05) lower than those of the peak levels. Serum F levels in both sex during dark phase were significantly (P<0.05) higher than those levels during daytime. A surge of serum OHP concentrations in both sexes was observed at the time of twilight (03:00). The peak time of serum T, 11KT and DHP levels were approximately 6 hours prior to those of serum F and OHP levels. Serum E2 in female and P in both sex fluctuated intensely during sampling period, and did not show remarkable changes. These results strongly suggest the existence of circadian-like diel changes in serum T, DHP, F and OHP levels in both sex and 11KT in male, and no variations in serum E2 in female and P in both sex in spermiated/ovulated Japanese char under the stage of final maturation. Furthermore, relationship between circadian rhythms of steroid hormones and spawning behaviors are discussed in the present study.
Yamada
Hideaki
H
School of Fisheries Sciences, Kitasato University, Sanriku, Iwate, Japan. hyamada@kitasato-u.ac.jp
Satoh
Ri-ichi
R
Ogoh
Masashi
M
Takaji
Keigo
K
Fujimoto
Yasufumi
Y
Hakuba
Takeshi
T
Chiba
Hiroaki
H
Kambegawa
Akira
A
Iwata
Munehico
M
D000818:Animals; D002940:Circadian Rhythm; D005260:Female; D012739:Gonadal Steroid Hormones / Q000097:blood*; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D011374:Progesterone / Q000031:analogs & derivatives / Q000097:blood; D013739:Testosterone / Q000031:analogs & derivatives / Q000097:blood; D013997:Time Factors; D014337:Trout / Q000097:blood* / Q000254:growth & development* / Q000502:physiology
D012739:Gonadal Steroid Hormones; D013739:Testosterone; D011374:Progesterone; D006854:Hydrocortisone