Pigment movements in fish melanophores: Morphological and physiological studies.

Cyclic adenosine monophosphate (cAMP) has been shown to cause pigment dispersion in amphibian and fish melanophores. Since pigment displacements in melanophores of Pterophyllum scalare are known to be accompanied by assembly and disassembly of microtubules, the effect of cAMP on this process was investigated. Melanophores of isolated scales were treated with cAMP in the presence of vinblastine, a potent antimicrotubular agent. During the initial phase of vinblastine action, cAMP as well as its dibutyryl derivative are capable of counteracting the inhibitory effects of vinblastine on pigment dispersion. In addition, cAMP retains the velocity of pigment dispersion at about the maximum level during 1 hour experiments. Pigment aggregation was unaffected by cAMP. Since pigment dispersion in Pterophyllum-melanophores is accompanied by assembly of microtubules, it is concluded that cAMP influences, at least in part, melanosome dispersion through facilitation of microtubule assembly. [ABSTRACT FROM AUTHOR]