tudy on sex steroid-binding proteins (with emphasize on ۱۷ -estradiol) in plasma of female and juvenile kutum (Rutilus frisii kutum)

A sex steroid-binding protein (SBP) that binds to ۱۷ b-estradiol with high affinity and moderate capacity was identified in the plasma of female and juvenile of kutum (Rutilus frisii kutum) sampled during the early stage of gonadal maturation in October and prior to spawning in March. Mean maximum specific binding (Bmax) and equilibrium dissociation constant (Kd) of the fish were as follows: In early stage of gonadal development (October), Bmax= ۵۸۰۰±۹۷۰ fmol E۲/m gprotein, Kd ۴.۱±۰.۶nM, and prior to spawning (March) Bmax= ۴۰۰۰±۸۹۵ fmol E۲/mgprotein, Kd ۲.۹±۰.۳nM. In juvenile sampled in October Bmax= ۱۶۰۰±۱۳۰ fmol E۲/mg protein, Kd ۲.۱±۰.۲n M and in March samples Bmax= ۳۵۰۰±۷۸۰ fmol E۲/mg protein, Kd ۲.۲±۰.۲nM. Plasma estradiol binding characteristics of the adult samples in October and March differed from the juvenile samples in having both Bmax and Kd significantly higher than juveniles. Plasma SBP levels displayed a moderate correlation with GSI (r۲= ۰.۵۲) and CF (r۲= ۰.۵۱) and a weak correlation with HSI (r۲ = ۰.۲۸). Affinity was moderately correlated with CF (r۲ = ۰.۶۸) and HIS (r۲ = ۰.۵۰). A strong correlation was obtained between Bmax and Kd, high Bmax values coincided with high Kd values and vice versa.

Keywords:

۱۷ -estradiol , Plasma , Sex steroid-binding protein , Kutum