Prolactin (PRL) was purified from anterior pituitary glands of adult toad (Bufo japonicus formosus) by extraction of acetone-dried pituitary powder with acid acetone and chromatography on DEAE-cellulose and Sephadex G-100. Purification was monitored by radioimmunoassay developed for bullfrog PRL. Toad PRL thus obtained is as potent as bovine PRL in promoting collagen synthesis in the bullfrog tadpole tail fin. HPLC of the toad PRL on a reverse-phase column shows that the preparation behaves as a homogeneous protein. The hormone has a molecular weight of 23,000 as determined by SDS gel electrophoresis. The isoelectric point is 5.5 as determined by analytical electrofocusing. The amino acid composition closely resembles that of bullfrog PRL.
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