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Surveys of the estrogenic activity in coastal areas of Japan were performed by using two serum vitellogenins (Vg-530 and Vg-320) of male Japanese common goby Acanthogobius flavimanus as biomarkers. To evaluate the relationship between the Vg concentrations in the serum of male fish and the concentrations of environmental estrogens in seawater, 3 week exposure experiments were performed using estradiol (E2), nonylphenol (NP) and bisphenol A (BPA). From the results of the E2 exposure, mean concentrations of the Vg and the ratio of Vg-positive fish increased from actual concentration at 10.5 ng/L E2 treatment. Exposure of NP and BPA showed that the 19.0 µg/L NP treatment induced the Vg but 133.7 µg/L BPA did not. As for the survey of the estrogenic activity in coastal areas, the mean Vg concentrations and ratio of Vg-positive fish in some urban areas were similar to values of the 10.5 ng/L E2 treatment. Although E2 and NP were detected in the seawater from urban areas, the concentrations were concluded as not sufficient to independently induce the Vg. Considering these results, it is concluded that the total estrogenic activity in some urban areas is dependent not only on E2 but synergistically with other environmental estrogens. [ABSTRACT FROM AUTHOR]

Because blood vitellogenin (Vg) has been considered a biomarker for environmental estrogens, the basal levels of Vg and 17β-estradiol (E2 ) were determined in male Japanese whiting reared under natural conditions. Serum levels of Vg and E2 were measured and gonadal development was assessed by gonadosomatic index (GSI) and histological observation in 8–10 male fish at monthly intervals throughout the annual reproductive cycle. Serum E2 was <60 pg/mL throughout the study period. In contrast, serum Vg exhibited seasonal changes: serum levels of Vg gradually increased from April to May (mean 63 ± 13 ng/mL and 124 ± 48 ng/mL in April and May, respectively), and then reached a peak value (mean 352 ± 68 ng/mL) in June. Thereafter, serum Vg gradually decreased, reaching undetectable levels (<50 ng/mL) in October. Serum levels of Vg tended to increase in the male fish in which the GSI was >1%. Histological observation revealed that testes in such male fish were in active spermatogenesis and then all of the testes of male fish in which serum Vg decreased to ND levels were regressed. These results suggest that Vg productive potency (sensitivity to estrogens) may increase in the spermatogenic stage, resulting in production of Vg in response to very low levels of natural or xenobiotic estrogens. [ABSTRACT FROM AUTHOR]

ABSTRACT: To determine the thermal limit for normal spawning of Japanese whiting and to evaluate thermal effects on spawning in the normal temperature range, two experiments were conducted. In Experiment 1, the temperature of three experimental groups (Groups A, B and C) was increased from 25 to 28, 31 or 33°C, respectively. Subsequently, temperatures in all groups were decreased to 28°C. During the experimental period, the number of eggs, egg size, and hatching rate were monitored. According to the results, the upper thermal limit of normal spawning was considered to be 28–29°C, because the number of eggs and the hatching rate decreased at temperatures over 28°C. However, egg size tended to be reduced at 28°C, and was found to be strongly dependent on temperature. In Experiment 2, the number of eggs, egg size and time of spawning were compared between fish held at a constant temperature of 22°C (Group CT) and those held at increasing temperatures from 22 to 28°C (Group IT). Group IT spawned more in number and had smaller-sized eggs than did Group CT, while spawning was delayed in group IT. To identify the thermal effects on spawning of Japanese whiting, the mechanisms governing egg size must be determined. [ABSTRACT FROM AUTHOR]

Two vitellogenins (Vgs) were detected in serum from estradiol-17β (E2)-injected Japanese common goby (Acanthogobius flavimanus). Vitellogenins with molecular masses of 530 kDa (Vg-530) and 320 kDa (Vg-320) were purified, and used to raise specific antisera in rabbits. Sandwich enzyme-linked immunosorbent assays (ELISAs) for Vg-530 and Vg-320 were developed using the antisera and the isolated Vgs. The sensitivity ranges of these ELISAs were 1.25–160 ng/ml for Vg-530 and 0.26–66 ng/ml for Vg-320, and very low cross-reactivity was found with the alternate Vg in each assay. Treatment of male gobys with E2 by injection and immersion induced both Vgs in sera in a dose-dependent manner. The mean concentrations of the Vgs increased from 10 ng/L E2 exposure for three weeks. Serum concentrations of the two Vgs in field-collected maturing females increased in accordance with increment of E2 level and ovarian development, and the mean concentrations of Vg-530 were higher than those of Vg-320 in maturing female. These results indicate that the sandwich ELISAs for Vg-530 and Vg-320 developed in the present study is useful as an assay system for surveys of estrogenic activity in coastal areas of Japan. [Copyright &y& Elsevier]