title: Microtubule--and microfilament--disrupting drugs and melanosome migration in melanophores of Papiliochromis ramirezi (Cichlidae, Teleostei).
abstract: We report here the effects of cytochalasin B, colchicine and vinblastine on melanosome migration in Papiliochromis ramirezi melanophores. Melanosome migration was not affected by 2 X 10(-5) M cytochalasin B. On the other hand, the aggregation, usually elicited by 10(-6) M norepinephrine, was completely inhibited by simultaneous treatment with 10(-3) M colchicine and cold (0-3 degrees C). Same results were obtained with 10(-3) M vinblastine. Lower concentrations of colchicine had no effect on granule aggregation. However, the aggregation in 50% of the melanophores was still blocked by 10(-5) M vinblastine, whereas 10(-7) M vinblastine was ineffective. Melanosome dispersion usually elicited by 10(-3) M theophylline was significantly accelerated by 10(-3) M colchicine, but delayed by 10(-3) M vinblastine. Lower concentrations of both agents had no effect on pigment dispersion. Therefore our results strongly suggest that microtubule structural integrity is essential to P. ramirezi melanosome displacements. As cytochalasin B had no effect on pigment migration, actin-like microfilaments might be either non-related to granule motion or absent in these chromatophores.
mesh_terms: D008841:Actin Cytoskeleton / Q000187:drug effects*; D000818:Animals; D002449:Cell Aggregation / Q000187:drug effects; D003078:Colchicine / Q000494:pharmacology*; D003571:Cytochalasin B / Q000494:pharmacology*; D003599:Cytoskeleton / Q000187:drug effects*; D005399:Fishes; D008544:Melanocytes / Q000502:physiology*; D008547:Melanophores / Q000378:metabolism*; D008870:Microtubules / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D010858:Pigmentation / Q000187:drug effects; D013806:Theophylline / Q000494:pharmacology; D014747:Vinblastine / Q000494:pharmacology*
chemical_list: D003571:Cytochalasin B; D014747:Vinblastine; D013806:Theophylline; D003078:Colchicine; D009638:Norepinephrine