Neuropeptide Y Inhibits Chromaffin Cell Nicotinic Receptor-Stimulated Tyrosine Hydroxylase Activity through a Receptor-Linked G Protein-Mediated Process
Abstract
Acetylcholine stimulation of bovine chromaffin cells results in increased norepinephrine and epinephrine secretion accompanied by a corresponding increase in synthesis. The addition of neuropeptide Y (NPY) to the culture medium prevents the increase in catecholamine synthesis but not secretion. Treatment of chromaffin cells with nicotine produces a concentration-dependent increase in tyrosine hydroxylase activity (IC50 = 1.2 μm) that is reduced if NPY is present during stimulation. Tyrosine hydroxylase activity decreases in a concentration-dependent fashion if increasing amounts of NPY are included in the culture medium, IC50 = 0.2 nm. Treatment with pertussis toxin completely prevents the effect of NPY. The rank order of potency for inhibition of tyrosine hydroxylase activity is NPY ≥ [Leu31,Pro34]NPY ≥ peptide YY > NPY2–36>NPY13–36 > NPY18–36 ≥ NPY26–36 ≫ NPY1–30, suggesting a NPY-Y1 receptor subtype. Examination of the effect of NPY on nicotine stimulation of chromaffin cell protein phosphorylation showed that NPY produces a concentration-dependent decrease in a 60-kDa protein, IC50 = 6.4 nm. The effect of NPY is pertussis toxin-sensitive. The rank order of potency is [Leu31,Pro34]NPY ≥ NPY ≫ NPY18–36. Immunoprecipitation confirmed the identity of the 60-kDa protein as tyrosine hydroxylase.
Footnotes
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Send reprint requests to: Terry D. Hexum, Ph.D., Department of Pharmacology, University of Nebraska Medical Center, Omaha, NE 68198-6260.
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↵1 J. Zheng and T. D. Hexum, unpublished observations.
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This work was supported by a grant from the National Institutes of Health Grant NS26479.
- Abbreviations:
- NPY
- neuropeptide Y
- PYY
- peptide YY
- KRP
- Krebs-Ringer phosphate
- DMEM
- Dulbecco’s modified Eagle medium
- SDS
- sodium dodecyl sulfate
- PAGE
- polyacrylamide gel electrophoresis
- ACh
- acetylcholine
- NE
- norepinephrine
- EPI
- epinephrine
- PTX
- pertussis toxin
- HEPES
- 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid
- ANOVA
- analysis of variance
- EGTA
- ethylene glycol bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid
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- Received March 13, 1997.
- Accepted September 4, 1997.
- The American Society for Pharmacology and Experimental Therapeutics
