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Benzo[a]pyrene (BaP) is generated by the incomplete combustion of organic substances such as oil and coal, and is a widespread organic environmental contaminant in terrestrial and aquatic ecosystems. To determine the effects of BaP on organisms, we investigated its time- and dose-related effects on the levels of cytochrome P4501A (P4501A) mRNA in the liver and gills of the olive flounder (Paralichthys olivaceus) using quantitative polymerase chain reaction (QPCR) and measured the plasma glucose, cortisol, aspartate aminotransferase (AST), and alanine aminotransferase (ALT) levels. The full-length olive flounder P4501A cDNA consists of 1566 nucleotides and encodes a 521-amino-acid protein. In the liver and gills, the expression of P4501A mRNA was highest 6 h after exposure to both 10 and 30 µg l-1 BaP, and then decreased. In addition, the plasma parameters increased with exposure. These results suggest that P4501A plays an important role in the detoxification of BaP, which stressed the olive flounder. Therefore, these physiological parameters may be indicators of BaP-induced stress responses. [ABSTRACT FROM AUTHOR]

We cloned complementary DNA (cDNA) encoding the arginine vasotocin receptor (AVT-R) from the kidney of olive flounder (Paralichthys olivaceus). Olive flounder AVT-R cDNA consists of 1155 bp, and encodes a protein of 384 amino acids. To investigate the stress responses and osmoregulatory abilities of olive flounder in changing salinities (35, 17.5, 8.75, 4, and 0 psu), we examined the expression of AVT-R, prolactin (PRL), and PRL receptor (PRL-R) messenger RNA (mRNA) in osmoregulatory organs using quantitative real time PCR (QPCR). AVT-R and PRL-R were expressed in the gill, kidney, and intestine, whereas PRL mRNA was expressed only in the pituitary gland. In addition, we measured the levels of plasma glucose, cortisol, aspartate aminotransferase (AST), and alanine aminotransferase (ALT). The mRNA expression and plasma parameters increased in hypoosmotic environments. Furthermore, osmolality decreased significantly according to salinity concentration decreased. These results suggest that AVT-R, PRL, and PRL-R mRNA play important roles in the hormonal regulation of osmoregulatory organs, thereby improving the osmoregulatory ability of olive flounder in hypoosmotic environments. [ABSTRACT FROM AUTHOR]