Potential molecular mechanisms underlying environmental disruption of the stress response endocrine system in wild flatfish of Southern California's urban ocean

Impairment of endocrine responses to stress in southern California marine fish has been linked to anthropogenic disturbances, such as exposure to environments impacted by wastewater treatment plants (WWTPs). In order to study the possible molecular mechanisms underlying this endocrine disruption, three key steroidogenic enzyme cDNAs involved in cortisol synthesis (StAR, P45011p, and 11j3-HSD-2) were cloned from interrenal tissue (contains cortisol steroidogenic cells) of English sole (Parophyrus vetulus) and hornyhead turbot (Pleuronichthys verticalis) and real-time quantitative PCR (qPCR) assays were developed. In English sole sampled from a WWTP outfall site, impaired cortisol responses were associated with significantly altered interrenal expression of all 3 genes, indicative of impaired steroidogenic capacity. In hornyhead turbot, highly reduced interrenal StAR mRNA expression relative to that in English sole was associated with severely diminished cortisol responses at all study sites. These studies point to potential molecular targets of endocrine-disrupting compounds present in southern California's marine environment.