Light-induced pigment aggregation in cultured fish melanophores: spectral sensitivity and inhibitory effects of theophylline and cyclic adenosine-3',5'-monophosphate.

About 20% of xiphophorin fish (Xiphophorus maculatus) dermal melanophores which were cultured in monolayer for 5 to 10 days responded to light directly, exhibiting reversible melanosome aggregation within a few minutes. In order to determine the spectral sensitivity for the light-response, absorbance changes due to the light-induced melanosome aggregation were measured on single melanophores in a range of wavelengths from 370 to 550 nm using a recording microspectrophotometer. The melanophores showed maximum sensitivity to a wavelength of about 410 nm and very little to those longer than 500 nm. 10(-4) to 10(-2) M theophylline and 10(-4) M cAMP had inhibitory effects on the light-response.