In this report we studied coupling of M2 and M4 muscarinic acetylcholine receptors to activation of endothelial nitric oxide synthase (eNOS). Chinese hamster ovary cells that co-express the individual receptor subtypes and eNOS in a stable fashion were used as a model. Activation of eNOS was assayed by measuring increasing levels of cyclic GMP in admixed cells that contain guanylate cyclase. Activation of both M2 or M4 muscarinic receptors resulted in marked activation of eNOS, in a time- and concentration-dependent manner. The time course of the response exhibited a transient peak, followed by a sustained lower plateau. While the sustained phase was dependent on influx of extracellular calcium, the transient response showed dependency on both mobilization of intracellular calcium and extracellular influx. (C) 2000 S, Karger AG, Basel.
- Endothelial nitric oxide synthase
- Guanylate cyclase
- Muscarinic acetylcholine receptors
- Nitric oxide
- Receptor function
- Receptor subtypes