The mRNA expression of P450 aromatase, gonadotropin beta-subunits and FTZ-F1 in the orange-spotted grouper (Epinephelus Coioides) during 17alpha-methyltestosterone-induced precocious sex change.
The orange-spotted grouper Epinephelus coioides is a protogynous hermaphroditic fish, but the physiological basis of its sex change remains largely unknown. In the present study, the 2-year-old orange-spotted grouper was induced to change sex precociously by oral administration of 17alpha-methyltestosterone (MT, 50 mg/Kg diet, twice a day at daily ration of 5% bodyweight) for 60 days. The serum testosterone levels were significantly elevated after MT treatment for 20 and 40 days as compared to control, but the levels of serum estradiol (E(2)) remained unchanged. The expression of P450aromA in the gonad significantly decreased after MT treatment for 20, 40, and 60 days. Accordingly, the enzyme activity of gonadal aromatase was also lower. The expression of FSHbeta subunit in the pituitary was significantly decreased after MT treatment for 20 days, but returned to the control levels after 40 and 60 days; however, the expression of LHbeta subunit was not altered significantly by MT treatment. The expression of FTZ-F1 in the gonad also decreased significantly in response to MT treatment for 40 and 60 days, but its expression in the pituitary was not altered significantly. Interestingly, when tested in vitro on ovarian fragments, MT had no direct effect on the expression of P450aromA and FTZ-F1 as well as the activity of gonadal aromatase, suggesting that the inhibition of gonadal P450aromatase and FTZ-F1 by MT may be mediated at upper levels of the brain-pituitary-gonadal axis. Taken together, these results indicated that FSH, P450aromA, FTZ-F1, and serum testosterone are associated with the MT-induced sex change of the orange-spotted grouper, but the cause-effect relationship between these factors and sex change in this species remains to be characterized.
Zhang
Weimin
W
Institute of Aquatic Economic Animals, School of Life Sciences, Zhongshan (Sun Yat-Sen) University, Guangzhou, P.R.China ls68@zsu.edu.cn
Zhang
Yong
Y
Zhang
Lihong
L
Zhao
Huihong
H
Li
Xin
X
Huang
He
H
Lin
Haoran
H
D000818:Animals; D001141:Aromatase / Q000235:genetics* / Q000378:metabolism; D001492:Bass / Q000097:blood / Q000235:genetics* / Q000502:physiology; D004958:Estradiol / Q000097:blood; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D006062:Gonadotropins / Q000235:genetics* / Q000378:metabolism; D006066:Gonads / Q000187:drug effects / Q000378:metabolism; D057850:Hermaphroditic Organisms; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D008297:Male; D008777:Methyltestosterone / Q000008:administration & dosage / Q000494:pharmacology*; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics* / Q000378:metabolism; D019849:Sex Determination Processes; D012733:Sex Differentiation / Q000187:drug effects / Q000235:genetics; D054339:Steroidogenic Factor 1; D013739:Testosterone / Q000097:blood; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
D006062:Gonadotropins; D018398:Homeodomain Proteins; D021122:Protein Subunits; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D054339:Steroidogenic Factor 1; D014157:Transcription Factors; D013739:Testosterone; D004958:Estradiol; D001141:Aromatase; D008777:Methyltestosterone