Pigment particle translocation in detergent-permeabilized melanophores of Fundulus heteroclitus

Abstract Melanophore preparations of Fundulus heteroclitus that have been treated with the detergent Brij 58 can aggregate their pigment in response to epinephrine. On the basis of several criteria, it appears that cell lysis occurs under the detergent conditions used. Electron microscopic examination of detergent-treated cells shows progressive disruption of the melanophore plasma membrane during the time in which pigment aggregation occurs. Brij-treated cells are accessible to ferritin, a large electron-dense probe that is effectively excluded from non-detergent-treated controls. In cells incubated with detergent, fixed, and treated first with rat monoclonal antibodies against tubulin and then with fluorescein-isothiocyanate-labeled goat anti-rat IgG, a characteristic radical pattern of microtubule staining can be visualized by fluorescence microscopy. Control preparations treated similarly, but without detergent, do not stain. Vanadate, an inhibitor of ciliary and flagellar dynein ATPase, blocks melanosome aggregation in response to epinephrine in detergent-treated preparations but has no effect on intact melanophores. erythro-9-[3-(2-hydroxynonyl)]Adenine, another inhibitor of dynein ATPase, also inhibits pigment aggregation in Fundulus melanophores. The possibility that a dynein-like molecule plays a role in pigment aggregation is discussed.