Alkylphenols impact on glycerophospholipids and cholesterol in female Atlantic cod liver and brain

This digital document is a journal article from Comparative Biochemistry and Physiology, Part C, published by Elsevier in 2007. The article is available in HTML format and can be accessed immediately after purchase through your Amazon.com Media Library, viewable with any web browser.

Offshore oil production releases large amounts of lipophilic compounds in the form of produced water into the ocean. In 2004, approximately 143 million m^3 of produced water, containing around 13 tons of long-chain (>C"4) alkylphenols (AP), was discharged from installations in the Norwegian sector of the North Sea. Long-chain APs are known to cause endocrine disruption in various species, but their long-term effects in the marine environment are not well understood.

In the present study, Atlantic cod (Gadus morhua) were exposed to a mixture (1:1:1:1) of APs (4-tert-butylphenol, 4-n-pentylphenol, 4-n-hexylphenol, and 4-n-heptylphenol) or 17 @b-estradiol (E2) at concentrations ranging from 0.02 to 80 mg AP/kg for 5 weeks. The study examined the effect of these exposures on the fatty acid profile and cholesterol content in the membrane lipids of the liver and brain. Additionally, the researchers investigated the interaction between different para-substituted APs and glycerophospholipids (native phospholipids extracted from cod liver and brain) and model phosphatidylcholine (PC 16:0/22:6 n-3) in monolayers using the Langmuir-Blodget technique.

The results showed that APs and E2 alter the fatty acid profile in the polar lipids (PL) from the liver, leading to an increase in the proportion of saturated fatty acids (SFA) and a decrease in n-3 polyunsaturated fatty acids (n-3 PUFA) compared to the control group. A similar effect was observed in the brain of the exposed groups, where the neutral lipids (mainly cholesterol ester) exhibited higher fatty acid saturation, but the polar lipids did not. Furthermore, the AP and E2 exposure resulted in a decline in the cholesterol levels in the brain.

The in vitro studies revealed that APs increase the mean molecular areas of the PLs in the monolayers at concentrations as low as 5 @mM, likely due to the intercalation of the APs between PL molecules. This increase in molecular area was found to be proportional to the length of the alkyl side chain.

These findings suggest that exposure to APs and E2 can have significant impacts on the fatty acid composition and cholesterol content in the lipid membranes of fish, which could potentially lead to broader physiological and ecological consequences in the marine environment. The study provides valuable insights into the interactions between lipophilic compounds and biological membranes, highlighting the need for further research on the long-term effects of produced water discharges in the marine ecosystem.

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