Uptake and depletion of plasma 17alpha-methyltestosterone during induction of masculinization in muskellunge, Esox masquinongy: effect on plasma steroids and sex reversal.
Oral administration of 17alpha-methyltestosterone (MT) was used to induce masculinization of sexually undifferentiated muskellunge, Esox masquinongy. Three groups of muskellunge (mean weight, 2.5 +/- 0.6 g) were submitted to MT treatment (15 mg of MT/kg) for 60 days. An additional one group was used as a control (hormone-free diet). Food was distributed over a 10-h period by using automatic belt feeders. Blood was sampled in both control and treated fish at different intervals during and after feeding: before (0 h), at 3 h, 6 h, and cessation of feeding (10 h), and after a fast of 22 h (32 h). MT had no significant effect on growth and survival in muskellunge 6 months after the treatment. Concentrations of plasma MT increased during the feeding period and reached their maximum levels 6 or 10 h after starting feeding. This rapid increase of MT indicated a rapid absorption of this steroid. Plasma MT levels then declined and reached a radir by 22 h after cessation of feeding, suggesting that MT is rapidly metabolized and excreted. The profiles of plasma testosterone during the MT treatment did not differ significantly between control and MT-treated groups. During and after the MT treatment, the concentration of plasma testosterone did not differ significantly between control and MT-treated groups. Moreover, no sexual dimorphism of testosterone levels was observed. Six months after treatment, the sex ratio in MT-treated groups (33% males, 62% females, and 5% intersex) was opposite to control (70% and 30%, respectively) and differed significantly. This suggests that at 15 mg of MT/kg over 60 days, a paradoxical feminization took place.
Rinchard
J
J
School of Natural Resources, The Ohio State University, Columbus 43210, USA.
Dabrowski
K
K
Garcia-Abiado
M A
MA
Ottobre
J
J
D000818:Animals; D012734:Disorders of Sex Development; D017859:Esocidae / Q000502:physiology*; D005260:Female; D008297:Male; D008777:Methyltestosterone / Q000097:blood* / Q000378:metabolism / Q000494:pharmacology; D012744:Sex Ratio; D012741:Sexual Maturation / Q000187:drug effects / Q000502:physiology*; D013237:Stereoisomerism; D013739:Testosterone / Q000097:blood
D013739:Testosterone; D008777:Methyltestosterone