AN EDEMATOGENIC PEPTIDE ISOLATED FROM Leptodactylus pentadactylus SKIN SECRETION

CORDEIRO, J.S., CARDI, B.A., CARVALHO, K.M.

Laboratório de Neurofarmacologia, Universidade Estadual do Ceará, Fortaleza, CE, Brazil

Objectives: The anuran skin secretions contain several compounds, such as enzymes, steroids, biogenic amines, alkaloids, proteins and peptides that play an important biological hole to anuran adaptation to environment and protection from predators and microorganisms. The aim of this study was to evaluate the ability of a new peptide from Leptodactylus pentadactylus skin to produce inflammatory edema in rat hind paw and to verify the mediators involved.

Methods and Results: The skin secretion, obtained by subcutaneous injection of 500µl adrenaline (100µg/ml), was diluted in bidestilated water (1:4, v:v), lyophilized and kept at -25°C. The edematogenic peptide (EP) was purified by HPLC using a C18 column (25x250 mm)(5 ml/min) (acetonitrile 0-40%, 30 min). Its amino acid sequence (Edman, 1950), performed by an Applied Biosystem sequencer, was determined: RVDL. Intraplantar injection of male Wistar rats with the EP (0.4, 0.8 and 2mg/kg, 0.1ml/paw) induced significant (p<0.05) paw edema with peak activity at 1 hour (increase in volume: EP 0.4 mg/kg = 1.02 ml ±0.13 vs. 0.11 ml ± 0.03 of control group). The injection of mepiramine (10mg/kg), methysergide (1mg/kg), HOE 140 (1mg/kg) and cyproheptadine (6mg/kg), 1h before intraplantar injection of EP (0,4 mg/kg) significantly inhibit (p<0.05, mepiramine 49%, methysergide 86%, HOE 140 64%, cyproheptadine 80%) the paw edema.

Conclusions: The present study provides a direct evidence of the ability of EP to induce hind-paw edema in rats and indicates a key role for serotonin and histamine in this response. Once the edema induced by substance was also inhibited by B2 antagonist, it is possible to suppose that EP could also act directly in this receptor or could be acting by the synthesis of bradykinin.

CORRESPONDENCE TO:

Bruno Andrade Cardi, Rua Monsenhor Dantas, 1931/402, Fortaleza, CE, CEP: 60310-220, Brasil, Email: bcardi@bol.com.br