Jisung Ryu

Serum and ultrastructure responses of common carp (Cyprinus carpio L.) during long-term exposure to zinc oxide nanoparticles

The uptake of nanoparticles by aquatic organisms such as fish has raised concerns about the possible adverse effects of nanoparticles (NPs). In this study, we aimed to evaluate the toxicological effects in juvenile common carp exposed to zinc oxide nanoparticles (ZnO-NPs) for 12 weeks. The carp were exposed to 0 (control), 0.1, 0.3, 0.8, and 2.4mg/L of ZnO-NPs under a flow-through exposure system. Fish were sampled at 0, 4, 8, and 12 weeks to test for zinc in the test water and blood, and biochemistry analysis; further, they were sampled at 12 weeks to observe ultrastructural changes in the liver, kidney, and gill. In the organic serum, changes in the glutamic pyruvic transaminase/alanine aminotransferase (GPT/ALT) and glutamic oxaloacetic transaminase/aspartate aminotransferase (GOT/AST) levels were significant, but changes in the lactate dehydrogenase (LDH) and alkaline phosphatase (ALP) levels were not significantly different across all exposure periods. In the inorganic serum, the magnesium (Mg), inorganic phosphorus (IP), sodium (Na(+)), and chloride (Cl(-)) levels were significantly different in the exposure group and across exposure periods. However, calcium (Ca) and potassium (K(+)) levels were not significantly different. In the enzyme serum, the glucose (GLU) level significantly increased for the highest exposure group, but the total cholesterol (TCHO), triglyceride (Tg), and total protein (TP) levels were not significantly different during the exposure period. Ultrastructural changes in the liver induced changes in the black granules (of various sizes) in the lysosomes, indistinct nucleus membrane, and non-spherical nucleus. In the kidney, some mild changes were observed in the size and number of the lysosomes in the renal tubule. Desquamation and hypertrophy of pavement epithelial cells and vacuolation in the cytoplasm of the chloride cells were observed in the gill. Nanoparticles were also observed in the red blood cells, cytoplasm of all tissues, and glomerulus of the kidney. The observed changes in the serum and tissues may provide useful information regarding environmental conditions and risk assessments of aquatic organisms.

Identification of estrogen-like effects and biologically active compounds in river water using bioassays and chemical analysis.

The Nackdong River is the longest river in South Korea and passes through major cities that have several industrial complexes, including chemical, electric, and petrochemical complexes, and municipal characteristics such as apartment complexes. Along the river, the Gumi region has an electric industrial complex and an apartment complex that may be possible point sources of xenoestrogens such as phenolic compounds. To identify the causative chemicals for estrogenic activity in the river water of this region, bioassay-directed chemical analysis was performed. All samples from six sampling sites (an upstream point: S1; hot spot points: S2-1, S2-2, and S2-3; and downstream points: S3, and S4) showed estrogenic activity in the E-screen assay, with bio-EEQs (17beta-E(2)-equivalent quantities) ranging from 25.35-677.15 pg/L. Samples from S2-2, the sampling point downstream of the junction of stream water, and domestic and industrial wastewater, contained the highest estrogenic activity. Since the bio-EEQ of the organic acid fraction (F2) of the S2-2 sample had the highest activity (823.25 pg-EEQ/L) and F2 may contain phenolic compounds, GC-MS analyses for phenolic xenoestrogens were conducted with the organic acid fractions of the river water samples. Six estrogenic phenolic chemicals, 4-NP, BPA, 4-t-OP, 4-t-BP, 4-n-OP, and 4-n-HTP, were detected, with the highest concentrations (I-EEQ) found in S2-2 (231.80 pg/L). Among these phenolic chemicals, 4-NP was the most potent estrogen (bio-EEF; 8.12 x1 0(-5)) and acted as a full agonist. Furthermore, 4-NP was present at levels (2.0 microg/L in S2-2) that can induce VTG induction in fish (>1 microg/L). In addition, we confirmed that river water (S2-2) significantly increased serum VTG levels in crucian carp (Carassius auratus) in a fish exposure experiment under laboratory conditions. Therefore, phenolic xenoestrogens, especially 4-NP, may be the main causative compounds responsible for the estrogenic effect on the Nackdong River.

Molecular cloning of cytochrome P4501A cDNA of medaka (Oryzias latipes) and messenger ribonucleic acid regulation by environmental pollutants

The sequence of cytochrome P4501A (CYP1A) cDNA of medaka (Oryzias latipes) was determined, and its messenger ribonucleic acid (mRNA) regulation by beta-naphthoflavone (betaNF) was evaluated. The determined cDNA sequence contained 2,349 base pairs (bp), and the open reading frame contained a total of 1,563 bp encoding 521 predicted amino acids. The induction of CYP1A mRNA in medaka was evaluated using reverse transcription-polymerase chain reaction. The concentration-dependent induction of CYP1A mRNA in the liver was observed after exposure to betaNF at nominal concentrations of 20, 100, and 500 microg/L for 2 d. Time-dependent changes of CYP1A mRNA levels were also observed in the liver, gill, gut, and caudal fin tissues of medaka exposed to 100 microg/L of betaNF for 7 d. Our results showed that the degree of CYP1A mRNA induction in the gill, gut, and caudal fin after exposure to betaNF was relatively higher than that in the liver, possibly because of low basal levels of CYP1A mRNA in the gill, gut, and caudal fin of nonexposed fish. The induction of medaka CYP1A mRNA was also observed after exposure to an environmental sample, landfill leachate. The CYP1A mRNA inductions in the gill, gut, and caudal fin were also higher than that in the liver as shown in the betaNF-treated groups. These results show that CYP1A mRNA determination in the gill, gut, and caudal fin, which are in direct contact with the polluted water, may become a useful method for monitoring CYP1A-inducible chemicals.

Distribution of perfluoroalkyl substances in water from industrialized bays, rivers and agricultural areas in Korea

Perfluoroalkyl substances (PFASs) have been found in water environment globally. However, the difference on occurrence profiles between PFASs in water from coastal areas and inland rivers or/and agricultural areas is still limited. In this study, the presence of thirteen PFASs in sixty-five surface water samples collected from coastal areas of three southeastern industrialized bays, four major rivers, and six rice field areas in Korea were analyzed. Total PFAS concentrations (ng/L) range from 0.22-73.9 (mean=22.1) for the major rivers, 0.54-3.19 (mean=1.77) for the rice field areas, and <LOQ-27.8 (mean=3.90) for the industrialized bays. The most frequently detected PFASs were perfluorooctanoic acid, PFOA (86.2%) for perfluorocarboxylic acids, PFCAs and perfluorooctance sulfonic acid, PFOS (78.5%) for perfluorosulfonic acids, PFSAs. Positive significant Pearson correlations were determined for PFNA and PFDA (p<0.01, r=0.91) and PFOA and PFNA (p<0.01, r= 0.72). The results of this study indicate a general ascending order of PFCAs, PFSAs and PFASs concentrations in six sampling site groups categorized by potential PFASs emission sources as non-source <agricultural source<“outer bay source”<“inner bay source”<municipal source<wastewater treatment plant (WWTP) discharge. Significant differences (Tukey post hoc test in ANOVA, p<0.05) in PFASs concentration in water samples from sampling sites that receive WWTP discharge than those from others were found. Despite a decreasing trend of PFASs contamination in surface water from Nakdong River basin after the restriction of manufacture and usage of PFOS and its related compounds in 2011 was determined in Korea, the results of this study demonstrate the continuing input of PFAS in Korean rivers, rice field areas and industrialized bays. The PFOS and PFOA concentrations in water were below the threshold for adverse health effects. This study provides information for a better understanding of PFASs and the ongoing input of PFASs in Korean aquatic environment.