Occurrence of Physalaemin in Extracts of the Skin of Physalaemus Fuscumaculatus and Its Pharmacological Actions on Extravascular Smooth Muscle

Methanol extracts of the skin of Physalaemus fuscumaculatus, a South American amphibian, contain a principle which potently stimulates extravascular smooth muscle and possesses a powerful vasodilator and hypotensive action in the dog and other mammals (Erspamer, Bertaccini & Cei, 1962).This principle, called physalaemin, has now been isolated in a pure form and its amino acid composition and sequence have been fully elucidated (Erspamer, Anastasi, Bertaccini & Cei, 1964; Anastasi, Erspamer & Cei, 1964).Physalaemin is an endecapeptide having the following amino acid sequence (I), which closely resembles that of eledoisin (Ii):( I) Pyr-Ala-Asp(OH)-Pro-Asp(NH2)-Lys-Phe-Tyr-Gly-Leu-Met-NH2 (II) Pyr-Pro-Ser-Lys-Asp(OH)-Ala-Phe-Ile-Gly-Leu-Met-NH2 (Pyr = pyroglutamyl)The structure proposed has been confirmed by synthesis (Bernardi, Bosisio, Goffredo & De Castiglione, 1964).This paper describes: the occurrence of physalaemin in the skin of different Physalaemus- fuscumaculatus batches and of different Physalaemus species; the occurrence of phy- salaemin-like polypeptides in the skin of other amphibians; a simple method for obtaining physalaemin in a biologically pure form and for separating it from other active polypeptides.occurring in the Physalaemus skin; and the main pharmacological actions of physalaemin on extravascular smooth muscle.As just stated, the skin of Physalaemus fuscumaculatus contains, in addition to phy- salaemin, at least two other peptides active on smooth muscle.A preliminary description of these peptides will also be given.METHODS Amphibian material.The Physalaemus material used in this study was as follows:(1) Fifty adult specimens captured near Tucuman (Argentina) in January 1959.The dried skins weighed together 4.8 g, and the average weight of a skin was 0.1 g.Thirty skins were extracted with 80% methanol,.