Chemical structure of angiotensin in the bullfrog Rana catesbeiana.

Crude bullfrog angiotensin was prepared by modified Boucher's procedures. The kidney extract was incubated in vitro with homologous plasma. Crude angiotension, 15 micrograms equivalent to [Asp1, Ile5]angiotensin II in rat vasopressor assay, was purified further by three steps by SEP-PAK C18 cartridge, SP-Sephadex column chromatography, and high-performance liquid chromatography on Finepak SIL C18 column. Amino acid analysis was done on 64 ng of the purified material after acid hydrolysis. The fluorescent peptide mapping technique was used to confirm the amino acid sequence. It is proposed that bullfrog angiotensin is [Asp1, Val5, Asn9]angiotensin I.