Improved method for purification of Xenopus laevis vitellogenin and demonstration of cross-reactivity among wide-range species by radioimmunoassay.

This study was performed to improve the purification of Xenopus vitellogenin and establish the radioimmunoassay. The procedure of purification consisted of ammonium precipitation, DEAE-Sephadex chromatography and Sephadex G-200 gel chromatography. Using this procedure, 934 mg vitellogenin was purified from 49 ml of estradiol treated female Xenopus plasma (about 19 mg/ml). Vitellogenins purified from male and female plasma after a single injection of estradiol showed good correspondence in electrophoretic patterns and amino acid compositions, indicating that vitellogenin synthesis in the male occurs in four different genes as in the female. The radioimmunoassay for vitellogenin was established using an antibody in the plasma obtained from rabbits injected with purified Xenopus female vitellogenin. The titer was 20,000 times dilution of the plasma, and the minimum detectable amount of vitellogenin was 0.1 microgram. The cross-reactivity of this antibody with newt vitellogenin was about 65% and that of chick 6%. The cross-reaction was also observed in female bullfrog plasma. Vitellogenin content was increased gradually during the first 6 days after injection of estradiol in female and the elevated level of vitellogenin dropped afterward.