Vol. 282, Issue 1, H363-H371, January 2002
Loss of cardiac sympathetic neurotransmitters in heart
failure and NE infusion is associated with reduced NGF
Fuzhong
Qin,
Raju S.
Vulapalli,
Suzanne Y.
Stevens, and
Chang-Seng
Liang
Departments of Medicine and Neurobiology and Anatomy, University of
Rochester Medical Center, Rochester, New York 14642
Sympathetic
neurotransmitters are diminished in cardiac efferent nerve endings in
congestive heart failure (CHF). Similar changes occur after exogenous
norepinephrine (NE) infusion. Since NE reduces nerve growth factor
(NGF) in cultured cardiomyocytes, we proposed to determine whether the
loss of noradrenergic transmitters in the failing heart is caused by
the NE-mediated reduction of NGF or its neurotrophic receptor tyrosine
kinase A (TrKA). Dogs were assigned to receive either rapid ventricular
pacing (225 beats/min) or NE infusion (0.5 µg/kg/min) for 8 wk.
Control animals received either cardiac pacing of 100 beats/min or
saline infusion. We measured NGF and TrKA proteins by Western blot and
immunocytochemistry and measured NGF and TrKA mRNAs by reverse
transcription polymerase chain reaction, neuronal catecholaminergic
histofluorescence, tyrosine hydroxylase-immunostained profiles, and
plasma NE. Rapid ventricular pacing produced CHF with increased plasma
NE, decreased myocardial NGF protein (0.61 ± 0.07 vs. 1.04 ± 0.04, P < 0.05), TrKA protein (0.75 ± 0.08 vs. 0.98 ± 0.06, P < 0.05), NGF and TrKA mRNAs
and reduced catecholaminergic histofluorescence (197 ± 23 vs.
485 ± 43, P < 0.05), and tyrosine hydroxylase
profiles (360 ± 51 vs. 773 ± 36, P < 0.05). Decreases in tissue NGF and TrKA protein were also noted by
immunocytochemistry. Similar changes occurred in NE-treated animals.
Tissue NGF and TrKA levels correlated closely with the noradrenergic
transmitter profiles. We conclude that cardiac NGF and TrKA are reduced
by rapid ventricular pacing and NE infusion, and that these changes
correlate with decreases of cardiac catecholaminergic and tyrosine
hydroxylase profiles. Findings indicate that decrease of cardiac
sympathetic transmitters in heart failure is associated with
NE-mediated reduction of NGF and TrKA.
nerve growth factor; norepinephrine; sympathetic efferent nerve
fibers