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Journal Article 
Specific binding of exogenous sex hormones and chemical substances to sex hormone-binding globulin (SHBG) in carp and rainbow trout 
Nagae, M; Suminami, Y; Kitagawa, H; Shiroyama, K; Ohkubo, N; Matsubara, T 
ISSN: 0399-0974 
The binding characteristics of sex hormone-binding globulin (SHBG), the most important transporter of sex steroids in blood, was investigated using various kinds of sex steroids in carp and rainbow trout in vivo and in vitro. In vitro binding assay using various kinds of sex steroids revealed androgens (T and 11-KT), estrogens (E2 and EE2) and progestins (17 alpha-P and 17 alpha,20 beta-DP) have a high affinity to SHBG. However, the affinity of estrone, cortisol, and bisphenol-A to SHBG was very low or none. In all three types of in vivo E2 administrations to immature male carp (repeated intraperitoneal injection, water immersion and oral administration), specific binding of E2 to SHBG was confirmed in male carp treated by water immersion and oral administration methods. However, no specific E2 binding to SHBG was observed in fish treated by repeated intraperitoneal injection. These results indicated that continuous exposure of exogenous sex steroids for fish induce the specific binding of them to SHBG in blood. 
SHBG; Sex hormones; E2; Carp; Rainbow trout