OVIDUCT 17-BETA-ESTRADIOL RECEPTOR IN THE FEMALE LIZARD, PODARCIS-SICULA-SICULA, DURING THE SEXUAL CYCLE - RELATION TO PLASMA 17-BETA-ESTRADIOL CONCENTRATION AND ITS BINDING-PROTEINS

In the oviparous lizard, Podarcis s. sicula, 17beta-estradiol binding molecules were characterized in the oviduct and plasma. In addition, their concentration was evaluated throughout the annual cycle.In the oviduct, a 17beta-estradiol receptor (ER) is present. It shows high affinity for ligand (4.9-7.0 x 10(-10) M). It is decreased by ovariectomy, and induced by 17beta-estradiol treatment. 17beta-estradiol causes also a ER shift from the cytosol into the nuclei. On sucrose gradient ER behaviour is consistent with the properties of ER obtained from other 17beta-estradiol target organs. At isoelectrofocusing the labeled 17beta-estradiol binding molecules fall into three pH ranges: 5.2-5.6, 7.0-7.7, 8,0-8.7.Nuclear filled ER significantly increases as oviduct grows. This supports an ER role in oviduct stimulation by 17beta-estradiol.In the plasma, 17beta-estradiol binding molecules show many physico-chemical and behavioural properties of steroid-binding proteins (SBPs).