SEX STEROID-BINDING PROTEINS IN THE PLASMA OF THE GREEN FROG, RANA-ESCULENTA - CHANGES DURING THE REPRODUCTIVE-CYCLE AND DEPENDENCE ON PITUITARY-GLAND AND GONADS

Sex steroid binding proteins (SSBP) have been reported in the plasma o f female and male Rana esculenta. In both sexes SSBP bind [H-3]estradi ol and [H-3]testosterone with medium-high affinity and high specificit y. Using ion-exchange chromatography SSBP resolve into two peaks eluti ng at 0.27 M (peak I) and 0.36 M (peak II) NaCl. Both peaks bind [H-3] estradiol and [H-3]testosterone equally well. Isoelectrofocusing showe d that peak I focused at pH 6.0 and 7.5, whereas peak II focused at pH 6.0. SSBP capacity for [H-3]estradiol and [H-3]testosterone changes t hroughout the reproductive cycle, showing low levels during the nonbre eding period and increasing levels during the breeding period. Hypophy sectomy and/or gonadectomy result in small changes in SSBP capacity. S hort-term steroid hormone treatment of gonadectomized animals does not modify SSBP capacity. (C) 1994 Academic Press, Inc.