Vol. 2, Issue 4 (2017)
Effect of Colchicine (mechanochemical response) on the melanophores of teleost fish: Rasbora elanga
Author(s): Rekha Yadav, AK Jain
Abstract: Chromatophores are the neurone-like cells containing pigment granules that are responsible for the brilliant colours of fish, amphibians, reptiles, and cephalopods. Many animals’ species are capable of undergoing changes in their colour as an adaptive behavioural response under the control of nervous endocrine systems, mediated by cell surface receptors on the plasma membrane of the chromatophores. Receptors causing pigment aggregation in melanophores have been shown to be linked to the Gi protein, whose activation results in a decrease in intracellular cAMP, while receptors that cause dispersion of the pigment are shown to be liked to Gs protein, whose activation results in an increase in cAMP. The chemical cycle involving a cascade of events such as enzyme activation and various substrate protein (PKA) phosphorylation (dispersion) or dephosphorylation (aggregation), initiates a mechanical cycle for long-range movements of pigment granules depending on polar microtubules and specific motor proteins such as kinesin or kinesin related peptides (dispersion) and dyneins (aggregation) that get bound to the pigment granules. Under investigation Rasbora elanga melanophores are endowed with β-adrenergic receptors and thus it is, likely that Ca2+ can also affect melanosome movements in melanophores. Among investigations indicating a positive role for microtubules are those using inhibitors of mitosis, for eg., colchicines and related alkaloids. Colchicine in the present study showed inhibitory effect on melanosome movements, in particular those in centripetal direction i.e., including aggregation. Subsequent dispersion of melanophores in PS a phosphodiesterase inhibitor appears to be consistent with respect to centrifugal migration of pigment in the melanophores.