Antibodies against progesterone receptor from chick oviduct. Cross-reactivity with mammalian progesterone receptors.

The highly purified, molybdate-stabilized '8-9-S' form of the chick oviduct progesterone receptor complexed with [3H]progesterone (Specific activity approximately equal to 10-12 nmol bound steroid/mg protein) was prepared according to the three-step method [Renoir et al. (1982) Eur. J. Biochem. 127,71-79] and 50-90 micrograms samples were injected into a goat and a rabbit. Specific antibodies were observed as early as 2 weeks following the first booster injection and increased considerably 12 weeks later after further booster injections. Results were similar in the two animals, with higher titers observed in the goat. Antibodies cross-reacted with the 'transformed' 4-S form of the chick oviduct progesterone receptor. They also cross-reacted with molybdate-stabilized 8-9-S progesterone receptors of mammalian species (obtained from MCF-7 human breast cancer cells and from rabbit and mouse uteri), suggesting some evolutionary conservation of steroid hormone receptors. No cross-reaction was observed with chick oviduct oestradiol receptor and with chick plasma transcortin (a non-receptor progesterone-binding protein).