H. Kan et al., SIGNAL-TRANSDUCTION MECHANISM(S) INVOLVED IN PROSTACYCLIN PRODUCTION ELICITED BY ACETYLCHOLINE IN CORONARY ENDOTHELIAL-CELLS OF RABBIT HEART, The Journal of pharmacology and experimental therapeutics, 282(1), 1997, pp. 113-122
The purpose of this study was to elucidate the mechanism by which acet
ylcholine (ACh) promotes prostacyclin (PGI(2)) production in cultured
coronary endothelial cells (CEC) of the rabbit heart. ACh-induced prod
uction of PGI(2), measured as immunoreactive 6-keto-PGF(1 alpha), was
enhanced by increasing the extracellular calcium (Ca++) concentration
and reduced by Ca++ depletion. The receptor-operated Ca++ channel bloc
ker SK&F96365, but not the voltage-dependent Ca++ channel blockers ver
apamil or nifedipine, attenuated ACh-induced 6-keto-PGF(1 alpha) produ
ction and the associated rise in cytosolic Ca++. Thapsigargin, which d
epleted Ca++ accumulation from the intracellular Ca++ store, did not p
revent the ACh-induced rise in cytosolic Ca++. In the absence of extra
cellular Ca++, ACh and ATP increased cytosolic Ca++ but did not alter
6-keto-PGF(1 alpha) production. In permeabilized CEC, guanosine 5'-O-(
3-thiotriphosphate) (GTP-gamma-S) but not ACh enhanced 6-keto-PGF(1 al
pha) synthesis. ACh increased 6-keto-PGF(1 alpha) production in the pr
esence of GTP-gamma-S. These effects of GTP-gamma-S were attenuated by
guanosine 5'-O-(2-thiotriphosphate). In the absence of extracellular
Ca++, ACh or ATP increased cytosolic Ca++ in cells permeabilized with
beta-escin and loaded with GTP-gamma-S; this effect was attenuated by
guanosine 5'-O-(2-thiotriphosphate). The effect of ATP but not ACh to
mobilize intracellular Ca++ or increase 6-keto-PGF(1 alpha) was inhibi
ted by pertussis toxin. The phospholipase C inhibitor D609, which atte
nuated ACh- and ATP-induced mobilization of intracellular Ca++, did no
t alter 8-keto-PGF(1 alpha) production. The NO synthase inhibitor N-mo
nomethyl-arginine also failed to alter ACh-induced 6-keto-PGF(1 alpha)
synthesis. These data suggest that, in CEC of the rabbit heart, ACh s
timulates prostacyclin production via a pertussis toxin-insensitive G
protein and by increasing the influx of extracellular Ca++ through a G
protein-independent receptor-operated Ca++ channel.