ESTROGEN AND PROGESTERONE RECEPTORS IN LIZARD PODARCIS-S-SICULA OVIDUCT - SEASONAL DISTRIBUTION AND HORMONAL DEPENDENCE

Both estradiol (ER) and progesterone (PR) receptors have been found in the oviduct of the lizard Podarcis s. sicula. Their concentrations ch ange according to the reproductive cycle and under different hormonal treatment. The estradiol receptor binds DES with high affinity (K-d = 4.4 +/- 6.9 x 10(-10) M) and low capacity (7.0 +/- 2.1 x 10(-10) M). T he progesterone receptor binds both H-3-progesterone and H-3-R5020 wit h high affinity (K-d = 1.2 +/- 2.2 x 10(-9) M) and low capacity (0.5 /- 2.2 x 10(-10) M). PR elution profile on DNA-cellulose shows two pea ks eluting at 0.15 M NaCl and 0.27 M NaCl for the cytosol and 0.14 M N aCl and 0.26 M NaCl for the nuclear extract. When analyzed by isoelect rofocusing, PR shows two peaks at pH 7.8-8.0 and 6.8-7.0. During the r eproductive cycle, the peak of occupied ER in the nuclei precedes the increase in occupied PR. This pattern suggests a sequential action of estradiol and progesterone on the oviduct. In fact, while estradiol is involved in oviduct growth in early spring, progesterone stimulates g landular activity in the mature oviduct. Long term estradiol treatment up-regulates nuclear occupied PR, but down-regulates it when administ ered in combination with progesterone. On the other hand, progesterone alone or in combination with estradiol, prevents 17 beta-estradiol ef fects on nuclear occupied ER. (C) 1994 Wiley-Liss, Inc.