Photoreceptor-specific proteins in the mammalian pineal organ: immunocytochemical data and functional considerations.
The mammalian pineal organ contains photoreceptor-specific proteins, whose distribution shows conspicuous variation among different species of mammals. Nevertheless, the following general conclusions can be drawn: immunoreactions for S-antigen and recoverin labeled more pinealocytes than the rod-opsin immunoreaction. The intensity of the recoverin- and S-antigen immunoreactions varied from cell to cell. alpha-Transducin immunoreaction was absent from the pineal organ of all mammals investigated with the exception of the blind mole rat. Immunoreaction for the cyclic GMP-gated cation channel was undetectable in the pineal organ of all mammals investigated. The functional significance of photoreceptor-specific proteins in the mammalian pineal organ remains unknown. It has been speculated that the S-antigen might be involved in adrenergic transduction mechanisms. To test this assumption, we have started to analyze calcium responses of single rat pinealocytes to norepinephrine stimulation using the Fura-2 technique. The cells were subsequently labeled by means of S-antigen immunocytochemistry. These combined investigations showed that variation in S-antigen immunoreactivity is not correlated with differences in the rapid calcium response to stimulation with norepinephrine. It remains to be determined whether cells displaying different intensities of the S-antigen immunoreaction show different cyclic AMP responses to noradrenergic stimulation. Investigations along this line should help to clarify further whether there is indeed a relation between the expression of S-antigen and noradrenergic transduction mechanisms in the mammalian pineal organ.
Schomerus
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C
Center of Morphology, Johann Wolfgang Goethe University, Frankfurt/Main, Germany.
Ruth
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P
Korf
H W
HW
D000818:Animals; D000941:Antigens / Q000032:analysis / Q000502:physiology; D019393:Arrestin; D002135:Calcium-Binding Proteins / Q000032:analysis / Q000502:physiology; D005136:Eye Proteins / Q000032:analysis / Q000502:physiology*; D051597:Hippocalcin; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D007473:Ion Channels / Q000032:analysis / Q000502:physiology; D008074:Lipoproteins; D008322:Mammals; D009419:Nerve Tissue Proteins; D010786:Photoreceptor Cells; D010870:Pineal Gland / Q000166:cytology* / Q000502:physiology*; D051603:Recoverin; D012160:Retina / Q000502:physiology; D012243:Rhodopsin / Q000032:analysis / Q000502:physiology; D012377:Rodentia; D015293:Transducin / Q000032:analysis / Q000502:physiology
D000941:Antigens; D019393:Arrestin; D002135:Calcium-Binding Proteins; D005136:Eye Proteins; D007473:Ion Channels; D008074:Lipoproteins; D009419:Nerve Tissue Proteins; C496731:RCVRN protein, human; D051603:Recoverin; D051597:Hippocalcin; D012243:Rhodopsin; D015293:Transducin