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 hyoroxylase 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.
ASJC Scopus subject areas
- Molecular Medicine