Effects of letrozole and 17 alpha-methyltestosterone on gonadal development in all-female triploid rainbow trout (Oncorhynchus mykiss)

摘要

The objective of this study was to reveal the molecular mechanisms involved in the exogenous androgen and aromatase inhibitor-induced gonadal masculinization of all-female triploid rainbow trout (RBT) populations. 17 alpha-methyltestosterone (MT) and letrozole (LET) were used for treatment. The female triploid (XXX) rainbow trout is an effective model to study the molecular mechanism of gonadal masculinization, owing to its tendency towards masculinization under natural conditions. The MT and LET were supplemented with a diet in ethanol at 1.5 mg/kg and 50 mg/kg of food. The treatments did not influence ovary development in female triploid RBT in the early stage (56-80 days post fertilization, i.e. dpf). However, LET could more successfully induce the morphological masculinization of gonads when compared with MT, from 94 dpf to 377 dpf. Gene expression in gonads was analysed after MT and LET treatment. The results showed that expression of male-specific genes (sdy, dmrt1, sox9 and amh) increased more significantly in the LET group than in the control and MT group, and expression of female-specific genes (cyp19a1a and foxl2) in LET group tended to decrease significantly. At 377 dpf, significant inhibition of female-specific genes was shown in the LET group, and male-specific gene expression increased to levels almost similar to that in diploid male samples. Our preliminary results suggest that the genes involved in gonadal development are pivotal factors in fish sex reversal, and aromatase inhibitor is a more effective inducer of masculinization when compared with androgen.