It is well characterized that melanophores in the tail fin of Xenopus laevis tadpoles are directly photosensitive. In order to better understand the mechanism underlying this direct photosensitivity, we performed a retinal analysis of the tail fins and eyes of Xenopus tadpoles at stages 51-56 using high performance liquid chromatography (HPLC). Following the extraction of retinoids by the formaldehyde method, a fraction containing retinal and/or 3,4-didehydroretinal isomers from the first HPLC analysis were collected. These isomers were then reduced by sodium borohydride to convert retinal and/or 3,4-didehydroretinal isomers into the corresponding retinol isomers to prepare for a second HPLC analysis. Peaks of 11-cis and all-trans 3,4-didehydroretinol were detected in the eyes and tail fins containing melanophores, but they were not detected in the tail fins without melanophores. The amounts of 11-cis and all-trans 3,4-didehydroretinol were 27.5 and 5.7 fmol/fin, respectively, and the total quantity of 3,4-didehydroretinal was calculated at approximately 5×106 molecules/melanophore. These results strongly suggest the presence of 11-cis and all-trans 3,4-didehydroretinal in melanophores of the tadpole tail fin, which probably function as the chromophore of photoreceptive molecules.
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1 February 2002
Identification of 3,4-Didehydroretinal Isomers in the Xenopus Tadpole Tail Fin Containing Photosensitive Melanophores
Keiko Okano,
Tadashi Oishi,
Yoko Miyashita,
Tsuneo Moriya,
Motoyuki Tsuda,
Toshiaki Irie,
Nobuo Ueki,
Takaharu Seki
3,4-didehydroretinal
chromophore of photoreceptive molecule
photosensitive melanophore
tadpole tail fin
Xenopus