Ca2+ mobilization in nontransformed ciliary nonpigmented epithelial cells.
To investigate the calcium second messenger system in nonpigmented epithelial (NPE) cells, we studied drug-dependent cytosolic free Ca2+ concentration ([Ca2+]i) transients in cultured nontransformed human and rabbit NPE cells with a fluorescent Ca2+ indicator, fura-2, and a digital video-imaging system. The main findings of this study were: (1) The basal [Ca2+]i was 141.9 +/- 1.2 nM (mean +/- standard error of the mean, n = 401) in humans and 157.0 +/- 1.4 nM (mean +/- SEM, n = 346) in rabbits. (2) Isoproterenol (10(-4) M) had little effect on [Ca2+]i mobilization in both species. Norepinephrine (10(-4) M) and epinephrine (10(-4) M) increased [Ca2+]i in 56% and 78% of rabbit NPE cells by 1.8- and 2.1-fold of basal [Ca2+]i, respectively, but induced little [Ca2+]i change in human NPE cells. Carbachol (10(-3) M) elicited significant [Ca2+]i increase (more than 3-4-fold of basal level) in about 60-70% of NPE cells in both species. Heterogeneity was seen in the cellular response to these agonists. (3) Norepinephrine-induced response was blocked by phentolamine (10(-5) M), and the effect of carbachol was blocked by atropine (10(-4) M). (4) Time course of norepinephrine-induced [Ca2+]i change was primarily monophasic. In contrast, [Ca2+]i transients induced by carbachol were mostly biphasic. (5) The duration of carbachol- or norepinephrine-induced responses were shortened by the chelation of extracellular Ca2+ without affecting other parameters of the reaction. This study confirms the presence of the calcium signaling system in cultured nontransformed human and rabbit NPE cells.
Department of Ophthalmology, Kyoto University Faculty of Medicine, Japan.
T
T
Ohuchi
N
N
Yoshimura
H
H
Tanihara
S
S
Kuriyama
S
S
Ito
Y
Y
Honda
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002478:Cells, Cultured; D002924:Ciliary Body / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D016257:Fura-2 / Q000378:metabolism; D006801:Humans; D008856:Microscopy, Fluorescence; D010277:Parasympathomimetics / Q000494:pharmacology; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011817:Rabbits; D015398:Signal Transduction
D000317:Adrenergic alpha-Antagonists; D000318:Adrenergic beta-Agonists; D010277:Parasympathomimetics; D002217:Carbachol; D002118:Calcium; D016257:Fura-2