The Nucleotide Content of the Octopus Photoreceptor Cells : No Changes in the Octopus Retina Immediately Following an Intense Light Flash

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The amounts of cyclic-guanosine monophosphate (cGMP) and cyclic-adenosine monophosphate (cAMP) in octopus retina were measured by competitive radioimmunoassay. The amounts of the respective di- and tri-phosphonucleotides, and of visual pigment (as retinal isomers), were determined by high-performance-liquid chromatography (HPLC). Unirradiated octopus retina contained 2.4±0.5 pmol of cGMP and 36±7.0 pmol of cAMP. When 27.6% of the visual pigment in the retina was converted into the meta-form by an intense light flash, the rapidly-frozen retina contained 2.3±0.9 pmol of cGMP and 32±4.0 pmol of cAMP : no significant changes from the unirradiated state . The molecular ratios of cGMP and cAMP to total visual pigment were estimated to be 1 / 1800 and 1/120, respectively. Assuming that all the cGMP and cAMP were contained only in the rhabdome, it was estimated that there are 1.6 molecules of cGMP and 24 molecules of cAMP per microvillus. The low content of cGMP in the microvillus and the absence of significant change in cGMP content on exposure to light lead us to conclude that cGMP is not the `intracellular messenger' of phototransduction in octopus photoreceptor cells.
社団法人日本動物学会の論文
1993-04-15