Estradiol-17beta stimulates gonadotropin
II expression and release in the protandrous male black porgy
Acanthopagrus schlegeli Bleeker: a possible role in sex change.
Du JL, Lee CY, Tacon P, Lee YH, Yen FP, Tanaka H, Dufour S, Chang
CF.
Department of Aquaculture, National Taiwan Ocean University,
Keelung 202, Taiwan, Republic of China.
The objective of the present study was to investigate the in
vivo effects of sex steroids (estradiol-17beta, E(2); testosterone,
T) and the nonaromatizable androgen 5alpha-dihydrotestosterone
(DHT) on the levels of gonadotropin II (GTH II) in plasma and
pituitary and on aromatase activity in 2-year-old male black porgy,
Acanthopagrus schlegeli, during the prereproductive season. Black
porgy GTH II and GTH II beta subunits were purified and anti-GTH
II beta serum was induced. A specific radioimmunoassay for black
porgy GTH II was developed. cDNA GTH II beta was also cloned from
a black porgy pituitary cDNA library for use as a probe for Northern
analysis.
Male fish were divided into eight groups (n = 64): control;
E(2) (3 doses, 2.4 ng, 72 ng, and 2.2 microg/g body weight); T
(2 doses, 72 ng and 2.2 microg/g body weight); and DHT (2 doses,
72 ng and 2.2 microg/g body weight). Fish were injected with the
respective vehicle or different doses of material on days 0, 8,
and 16. Plasma was collected at 4-day intervals from days 4 to
20. Plasma GTH II concentrations were significantly increased
(up to 45-fold) in the E(2) group from days 4 to 20 in a dose-dependent
manner. In a further experiment during the late reproductive season,
plasma GTH II levels increased at 4 h and on days 1 and 2 following
a single injection of 1.0 microg E(2)/g body weight (on day 0).
Androgens (T or DHT) had little or no effect on plasma GTH II.
Pituitary GTH II contents on day 20 were significantly lower in
the 72-ng E(2) and 2.2-microg E(2) groups but not in the 2.4-ng
E(2) group compared with the control group.
Pituitary GTH II beta mRNA levels were significantly stimulated in the 72-ng and 2.2-microg
E(2) groups on day 20. Gonadal aromatase activity was not significantly
changed in any of the treated or control groups. It is concluded
that GTH II secretion in black porgy is regulated by an estrogen-specific
effect. Increased plasma GTH II levels or other factors in addition
to E(2) might be involved in the regulation of gonadal aromatase
activity and sex change in protandrous black porgy. Copyright
2001 Academic Press.
Sex Change Publications
|
Welcome to The
Reed Centre for Genital Surgery / 
Visit Dr. Reed's Other Sites: