Chromatic effects of endothelin family peptides in non-innervated fish, Synbranchus marmoratus, melanophores.
The biological activity of endothelins (ETs) in non-innervated Synbranchus marmoratus melanophores was demonstrated. These peptides induced a dose-dependent pigment aggregation (lightening skin) in these cells. However, they presented EC50's (effective concentration required to produce 50% of response) 26, 106 and 35 times higher than, respectively, the melanin concentrating hormone (MCH) EC50, and exhibited a characteristic temporal and dose-dependent autodessensibilization of the aggregative effect on the melanophores of this fish. The receptor characterization suggested the presence of the ET(B) subtype, since BQ-788 (selective antagonist of ET(B)) but not BQ-485 (selective antagonist of ET(A)) blocked the aggregative effect of the hormones. Confirming these data, sarafotoxin (SRTX) S6c, a toxin selective for ET(B), induced maximal aggregation of pigment granules. S6c presented an EC50 6.8 times higher than the MCH EC50, and 3.9, 15.6 and 5.1 times lower than the EC50's ETs, respectively. The melanotropic effect of SRTX S6b and vasoactive intestinal contractor (VIC) were demonstrated for the first time in this work. SRTX S6b induced a dose-dependent pigment aggregation and presented an EC50 2.54 and 17.2 times higher than the S6c and MCH EC50's, respectively. Compared to the ETs it was 1.53, 6.19 and 2.03 times lower, respectively.
Ramanzini
Guilherme Corrêa
GC
Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil.
Filadelfi
Ana Maria Caliman
AM
Visconti
Maria Aparecida
MA
D000818:Animals; D003116:Color; D016232:Endothelins / Q000145:classification / Q000378:metabolism*; D029941:Fish Proteins / Q000378:metabolism*; D008547:Melanophores / Q000187:drug effects / Q000378:metabolism*; D023701:Smegmamorpha / Q000378:metabolism*; D013997:Time Factors; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014757:Viper Venoms / Q000494:pharmacology
D016232:Endothelins; D029941:Fish Proteins; D014662:Vasoconstrictor Agents; D014757:Viper Venoms; C057354:sarafotoxins s6