Vitellogenin induction in male Japanese medaka exposed to the chemotherapeutics: oxytetracycline, Romet-30, and copper sulfate

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Date
2006-02-27
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Virginia Tech
Abstract

The specificity of a medaka vitellogenin (Vtg) enzyme-linked immunosorbent assay (ELISA) kit was tested on adult hybrid tilapia to determine if vitellogenin could be successfully measured in tilapia using this method. Adult hybrid (Orechromis niloticus x Oreochromis mossambicus x Oreochromis aureus) tilapia were injected with 17â-estradiol (E2) at 5 ìg/g body weight (b.w.) in two separate experiments and exposed to 2.5 ìg/g b.w. E2 through aquaria water in a third experiment. All fish were exposed to solvent controls (50/50 PBS/ethanol, or 59/41 PBS/ ethanol) proportional to the volume of estradiol solvent used. Experiment 1 was terminated due to a decrease in fish health and unexpected mortalities. Experiment 2 was continued though there was again a decrease in fish health and mortalities before experiment was completed. According to one-way ANOVA, Experiment 2 treatment groups were significantly different (P<0.05); however, Tukey's pairwise comparisons showed no differences between treatment groups. Experiment 3 results showed statistical differences between some treatment groups (P<0.001). However, maximum vitellogenin levels reached 1250 ng/mL Vtg, which were much lower than induced vitellogenin levels from literature (0.002 mg/mL to 6 mg/mL). Typical induction trends should be as follows: male control<female control< induced male<induced female; however, these trends were not observed in this study. For these reasons, the medaka vitellogenin ELISA kit was determined not specific to tilapia vitellogenin. This research was performed due to the fact that tilapia are farmed worldwide, and to increase research with these fish, in order to better understand their response to xenobiotic chemicals, easier methods are desired for measuring their vitellogenin.

Vitellogenin induction from exposure to the chemotherapeutics: oxytetracycline, Romet-30®, and copper sulfate was evaluate using Japanese medaka (Oryzias latipes). Medaka were exposed to E2 (0.0552 ìg/L) in aquaria water as a positive control. Medaka were fed oxytetracycline medicated feed at 0.0174 g, 0.0348 g, and 0.087 g, and Romet-30® medicated feed at 0.0261 g, 0.0522 g, and 0.1305 g daily for 11 days and 5 days as recommended. Medaka were exposed to copper sulfate at 1.85 mg/L for one hour (for 1 day, 7 consecutive days, and every three to five days for a total of 7 doses). Vitellogenin levels were measured using a sandwich ELISA. As expected, Vtg levels were induced from exposure to E2 (P<0.01); however, exposure to the chemotherapeutic compounds did not induce elevated Vtg levels. Alternately, copper sulfate exposure for one hour for 1 day did show a significant decrease in vitellogenin (P<0.01). Biological variation accounted for large portions of the variation within treatment groups in medaka vitellogenin in fish exposed to chemotherapeutics (as high as 41.01%). From this research we suggest that these chemicals do not have estrogenic properties capable of inducing vitellogenin in medaka.

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Romet-30, vitellogenin, copper sulfate, medaka, oxytetracycline
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