Calcium oscillations in a subpopulation of S-antigen-immunoreactive pinealocytes of the rainbow trout (Oncorhynchus mykiss).
By means of the fura-2 technique and image analysis the intracellular concentration of free calcium ions [Ca2+]i was examined in isolated rainbow trout pinealocytes identified by S-antigen immunocytochemistry. Approximately 30% of the pinealocytes exhibited spontaneous [Ca2+]i oscillations whose frequency differed from cell to cell. Neither illumination with bright light nor dark adaptation of the cells had an apparent effect on the oscillations. Removal of extracellular Ca2+ or application of 10 microM nifedipine caused a reversible breakdown of the [Ca2+]i oscillations. Application of 60 mM KCl elevated [Ca2+]i in 90% of the oscillating and 50% of the non-oscillating pinealocytes. The effect of KCl was blocked by 50 microM nifedipine. These results suggest that voltage-gated L-type calcium channels play a major role in the regulation of [Ca2+]i in trout pinealocytes. Experiments with thapsigargin (2 microM) revealed the presence of intracellular calcium stores in 80% of the trout pinealocytes, but their role for regulation of [Ca2+]i remains elusive. Treatment with norepinephrine (100 pM-50 microM), previously shown to induce calcium release from intracellular calcium stores in rat pinealocytes, had no apparent effect on [Ca2+]i in any trout pinealocyte. This finding conforms to the concept that noradrenergic mechanisms are not involved in signal transduction in the directly light-sensitive pineal organ of anamniotic vertebrates.
Kroeber
S
S
Center of Morphology, Section on Neurobiology, Johann Wolfgang Goethe-University, Frankfurt/Main, Germany.
Schomerus
C
C
Korf
H W
HW
D000818:Animals; D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D015220:Calcium Channels / Q000032:analysis; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D005260:Female; D016257:Fura-2; D006651:Histocytochemistry; D007150:Immunohistochemistry; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D008856:Microscopy, Fluorescence; D009638:Norepinephrine / Q000494:pharmacology; D017686:Oncorhynchus mykiss; D010507:Periodicity; D010802:Phylogeny; D010870:Pineal Gland / Q000737:chemistry / Q000166:cytology* / Q000294:innervation; D009418:S100 Proteins / Q000276:immunology; D013566:Sympathomimetics / Q000494:pharmacology
D015220:Calcium Channels; D009418:S100 Proteins; D013566:Sympathomimetics; D002118:Calcium; D016257:Fura-2; D009638:Norepinephrine