O,p'-DDT induction of vitellogenesis and its inhibition by tamoxifen in Nile tilapia (Oreochromis niloticus).
In order to investigate the mechanism by which o,p'-DDT disrupts endocrine functioning of Nile tilapia in vivo, the estrogenicity of o,p'-DDT was investigated in conjunction with 17beta-estradiol (E2) and tamoxifen. Mature, male tilapia were treated intraperitoneally with o,p'-DDT (60 mg/kg, one dose) or E2 (5 mg/kg, four doses) in the presence or absence of tamoxifen (5 mg/kg, six doses) for 12 days and then plasma vitellogenin (Vtg) (measured as alkaline-labile phosphorous), E2, and testosterone (T) were measured. Vtg levels were increased dramatically by E2 (1,744 +/- 171 microg/ml) and moderately by o,p'-DDT (82 +/- 15 microg/ml) compared with controls (23 +/- 3.5 microg/ml). Tamoxifen alone had no effect on Vtg production, but inhibited both E2 and o,p'-DDT stimulated vitellogenesis. T levels were reduced with E2 administration (1,688 +/- 383 pg/ml) and declined further with the combined treatment of E2 and tamoxifen (281 +/- 70 pg/ml), compared with controls (6,558 +/- 1,438 pg/ml). Tamoxifen or o,p'-DDT alone did not affect T levels, but their combined treatment did (2,069 +/- 647 pg/ml). The results of this study suggest that o,p'-DDT is weakly estrogenic in male tilapia, and that this activity may be mediated through the estrogen receptor.
Leaños-Castañeda
Olga
O
Departamento de Recursos del Mar, CINVESTA V Unidad Mérida, Yucatán, Mexico. olgalidia09@yahoo.com
Van Der Kraak
Glen
G
Lister
Andrea
A
Simá-Alvarez
Raúl
R
Gold-Bouchot
Gerardo
G
D000818:Animals; D023681:Cichlids / Q000502:physiology*; D003634:DDT / Q000009:adverse effects*; D004703:Endocrine System / Q000187:drug effects; D004965:Estrogen Antagonists / Q000494:pharmacology*; D007274:Injections, Intraperitoneal; D007306:Insecticides / Q000009:adverse effects*; D008297:Male; D011960:Receptors, Estrogen / Q000502:physiology; D013629:Tamoxifen / Q000494:pharmacology*; D014818:Vitellogenesis / Q000187:drug effects*
D004965:Estrogen Antagonists; D007306:Insecticides; D011960:Receptors, Estrogen; D013629:Tamoxifen; D003634:DDT