Teleost-type angiotensin is present in Australian lungfish, Neoceratodus forsteri

Angiotensin I (ANG I) was produced from the incubation of lungfish plasma w ith homologous kidney extracts. The purified peptide was found to have the sequence of H-Asn-Arg-Val-Tyr-Val-His-Pro-Phe-Thr-Leu-OH which is homologou s for the first eight residues with all teleost angiotensins so far sequenc ed, although lungfish generally possess tetrapod-type hormones. The lungfis h decapeptide (ANG I) induced dose-dependent increases in arterial pressure in the rat. The lungfish octapeptide (ANG II) released aldosterone from ki dney-adrenal tissue in vitro in a dose-dependent manner and induced dose-de pendent increases in arterial pressure of the lungfish. Substitution of asp aragine with aspartic acid in the first position (tetrapod-type ANG II) did not alter the blood pressure response significantly, but a second substitu tion of the valine in the (5)-position with isoleucine (ANG II form found i n human and rat) abolished the rise in arterial pressure in lungfish over t he same dose range, (C) 1999 Academic Press.