Expression profiles of hepatic vitellogenin and gonadal zona pellucida subtypes in gray mullet (Mugil cephalus) with 17α-ethinylestradiol-induced gonadal abnormality.

The subtypes of zona pellucida (zp), primarily expressed in female gonads, are considered novel molecular markers for testis-ova (or intersex), a type of gonadal abnormality caused by environmental estrogens (EEs) in Japanese medaka (Oryzias latipes). However, the association between testis-ova and the expression of gonadal zp subtypes is unclear in other teleost species, particularly in species studied in field surveys. In this study, 17α-ethinylestradiol (EE2) was orally administrated at 4-4000 ng/g body weight (BW)/day for 28 days to gray mullets (Mugil cephalus), and gonadal abnormalities were studied using histological analysis. The expression profiles of gonadal zp subtypes (zpb and zpc5) were analyzed to evaluate their suitability as gonadal abnormality markers by comparing with a hepatic vitellogenin (vtg) subtype (vtgAb). The oral administration of EE2 40 and 400 ng/g BW/day for 28 days induced significant gonadal zpb expression, and the gonads showed moderate abnormality (testis-ova). Conversely, the gonadal zpc5 levels decreased significantly in response to the oral administration of EE2 at 4000 ng/g BW/day for 28 days, and the gonads exhibited severe abnormalities. The hepatic vtgAb levels increased upon EE2 treatment regardless of gonadal abnormality. Therefore, the gonadal zpb levels and hepatic vtgAb levels served as appropriate markers for testis-ova and EE2 presence, respectively. However, the diagnosis of severe gonadal abnormality using gonadal zpc5 was moderately accurate. The findings suggest that the combination of vtgAb, zpb, and zpc5 is a potential marker for gonadal abnormality caused by EE contamination in gray mullet. That said, the potential of zpc5 should be reconsidered to determine if it shows greater accuracy in a larger or more diverse population.