Endothelin-induced changes of second messengers in cultured human ciliary muscle cells.
OBJECTIVE
To characterize the pharmacology of endothelin-induced changes in phospholipase C (PLC) activity, intracellular calcium concentration ([Ca2+]i) and cyclic adenosine monophosphate (cAMP) in cultured human ciliary muscle (HCM) cells.


METHODS
Changes in PLC activity of HCM cells were determined by production of [3H] inositol phosphates. [Ca2+]i was determined by single-cell dynamic fluorescence ratio imaging. Radioimmunoassays were used to determine cAMP and prostaglandin E2 (PGE2) concentrations.


RESULTS
Endothelin-1 (ET-1) stimulated PLC (mean EC50 = 335 pM) and activated calcium mobilization in HCM cells. These effects were mediated by the endothelin ETA receptor subtype because at ETB receptor-selective agonist, sarafotoxin S6c, was ineffective. Additionally, effects of ET-1 were inhibited by pretreatment with a selective ETA agonist, BQ610 (mean pKi = 9.96 for PLC). ET-1 also stimulated the production of PGE2 (mean EC50 = 12.0 nM) and cAMP (mean EC50 = 5.2 nM) by these cells. PGE2 appeared to mediate the stimulatory effect of ET-1 on adenylyl cyclase because blockade of ET-1-induced PGE2 production by 10 microM indomethacin also completely blocked the ET-1-activated cAMP production.


CONCLUSIONS
ET-1 stimulated PLC and increased [Ca2+]i in HCM calls by the ETA receptor subtype. ET-1 also increased cAMP production, an effect likely mediated by the enhanced production of prostaglandins.
Matsumoto
S
S
Department of Pharmacology, North Texas eye Research Institute, University of North Texas, Health Science Center at Fort Worth, USA.
Yorio
T
T
Magnino
P E
PE
DeSantis
L
L
Pang
I H
IH
D000262:Adenylyl Cyclases / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002924:Ciliary Body / Q000187:drug effects / Q000378:metabolism*; D000242:Cyclic AMP / Q000096:biosynthesis; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D015232:Dinoprostone / Q000378:metabolism; D016232:Endothelins / Q000494:pharmacology*; D005456:Fluorescent Dyes / Q000378:metabolism; D016257:Fura-2 / Q000378:metabolism; D006801:Humans; D007213:Indomethacin / Q000494:pharmacology; D007295:Inositol Phosphates / Q000096:biosynthesis; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009842:Oligopeptides / Q000494:pharmacology; D017466:Receptors, Endothelin / Q000187:drug effects / Q000378:metabolism*; D015290:Second Messenger Systems; D010738:Type C Phospholipases / Q000378:metabolism; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014757:Viper Venoms / Q000494:pharmacology
D016861:Cyclooxygenase Inhibitors; D016232:Endothelins; D005456:Fluorescent Dyes; D007295:Inositol Phosphates; D009842:Oligopeptides; D017466:Receptors, Endothelin; D014662:Vasoconstrictor Agents; D014757:Viper Venoms; C057354:sarafotoxins s6; C087220:BQ 610; D000242:Cyclic AMP; D010738:Type C Phospholipases; D000262:Adenylyl Cyclases; D015232:Dinoprostone; D002118:Calcium; D016257:Fura-2; D007213:Indomethacin