The effect of unoprostone isopropyl on Ca2+ release-activated Ca2+ currents in cultured monkey trabecular meshwork cells and ciliary muscle cells.
OBJECTIVE
The aim of this study was to investigate the effect of unoprostone isopropyl (UF- 021) on Ca2+ release-activated Ca2+ (CRAC) currents in cultured monkey trabecular meshwork (TM) cells and to compare the inhibitory effects on CRAC in cultured monkey ciliary muscle (CM) cells.


METHODS
Both TM and CM cells were isolated from monkey eyes, and each was grown in monolayer cell cultures. To measure changes in intracellular Ca2+ concentrations ([Ca2+]i), both types of cells were labeled with fluo-3 acetoxymethylester (AM) as a calcium indicator for 30 min at 25 degrees C and imaged with a confocal laser scanning microscope. After depletion of the intracellular Ca2+ stores with 1 microM thapsigargin and 1 mM EGTA containing Ca2+-free external solution, exposure to 2 mM Ca2+-containing external solution induced a sudden increase in [Ca2+]i, which was defined as the CRAC current.


RESULTS
In both TM and CM cells, CRAC currents were observed and were well suppressed by unoprostone-free acid (M1 metabolite). In the TM cells, 3 microM M1 metabolite suppressed the CRAC current. In contrast, in the CM cells, the CRAC current was suppressed by 100 microM M1 metabolite, but not by 10 microM or less. The half maximal inhibition concentration of M1 metabolite was 24.8+/-9.8 microM in TM cells and 183+/-30.6 microM in CM cells.


CONCLUSIONS
These findings indicate that there are CRAC channels in both TM and CM cells, and the influx of [Ca2+]i through the CRAC channels is suppressed by M1 metabolite. The inhibitory effect of M1 metabolite on CRAC currents was more prominent in TM cells than in CM cells. Suppression of the Ca2+ influx through CRAC channels by M1 metabolite is thought to regulate muscle tone in TM and CM cells. Therefore, CRAC inhibition by M1 metabolite may contribute to reduction of intraocular pressure.
Shimura
Masahiko
M
Department of Ophthalmology, NTT East Japan Tohoku Hospital, and Department of Ophthalmology and Medical Sciences, Tohoku University Graduate School of Medicine, Miyagi, Japan. masahiko@oph.med.tohoku.ac.jp
Yasuda
Kanako
K
Nakzawa
Toru
T
Kashiwagi
Kenji
K
D000814:Aniline Compounds / Q000378:metabolism; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology; D002478:Cells, Cultured; D002924:Ciliary Body / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D015237:Dinoprost / Q000031:analogs & derivatives* / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000378:metabolism; D007429:Intraocular Pressure / Q000187:drug effects; D008252:Macaca fascicularis; D018613:Microscopy, Confocal; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology; D014129:Trabecular Meshwork / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D014966:Xanthenes / Q000378:metabolism
D000814:Aniline Compounds; D000959:Antihypertensive Agents; D015220:Calcium Channels; D004791:Enzyme Inhibitors; D005456:Fluorescent Dyes; D014966:Xanthenes; C059715:Fluo-3; D004533:Egtazic Acid; C072630:isopropyl unoprostone; D019284:Thapsigargin; D015237:Dinoprost; D002118:Calcium