Measurements of light transmission through single melanophores

A photometrical method has been developed that allows assessment of subcellular pigment migration in melanophores of the fish cockoo wrasse (Labrus ossifagus L.) The pigment migration was studied with local light spot transmission measurements. Depending on where the light beam is placed on the melanophores it is possible to study events within an area of approximately 75 microns 2. Measuring pigment translocation in different parts of a melanophore gives new possibilities to study how cell membrane receptor-mediated signals are spread within a single cell, which will increase our understanding of how receptor activating drugs exert their cellular effect. The technique can be used in pharmacological and biophysical studies and in biosensors, pharmaceutical screens, environmental detectors, etc. The method clearly has the ability to study local and small changes in light transmission due to displacement of melanophore pigment granules. Since one melanophore on the tip of an optical fibre would be enough to obtain a measurable effect, the presented technique provides the basis for future development of biosensors small enough for in vivo applications, e.g., to monitor the catecholamine levels of circulating blood.