Ca(2+)-regulated nitric oxide generation in rabbit parotid acinar cells.

Area of Science:

• Biochemistry
• Cell Biology
• Physiology

Background:

• Muscarinic cholinergic agonists like methacholine influence salivary gland function.
• Calcium ions play a crucial role in cellular signaling pathways.
• Nitric oxide (NO) is an important signaling molecule with diverse physiological roles.

Purpose of the Study:

• To investigate the mechanism of nitric oxide (NO) generation in rabbit parotid acinar cells.
• To identify the specific type of nitric oxide synthase (NOS) involved and its regulation.
• To elucidate the role of intracellular calcium in methacholine-induced NO production.

Main Methods:

• Measurement of intracellular Ca(2+) concentration and NO generation.
• Use of Ca(2+)-mobilizing reagents and extracellular Ca(2+) removal.
• Immunoblot analysis and immunofluorescence microscopy for NOS detection.
• Purification and characterization of NOS enzyme activity.

Main Results:

• Methacholine increased intracellular Ca(2+) and NO generation in parotid acinar cells.
• Ca(2+)-mobilizing agents mimicked methacholine's effect on NO production.
• Extracellular Ca(2+) removal inhibited methacholine-induced NO generation.
• Neuronal NOS (nNOS) was identified in the cytosol of parotid acinar cells.
• Purified NOS was NADPH- and tetrahydroxybiopterin-dependent, activated by Ca(2+)/calmodulin.

Conclusions:

• NO is generated in rabbit parotid acinar cells via activation of neuronal NOS (nNOS).
• nNOS activation is regulated by intracellular Ca(2+) increases.
• Muscarinic receptor activation leads to Ca(2+)-dependent NO production in salivary glands.