Interstitial norepinephrine concentrations in skeletal muscle of ischemic heart failure.
During exercise, sympathetic nerve responses are accentuated in heart failure (HF), and this enhances norepinephrine (NE) release and evokes vasoconstriction. Two key pathophysiological responses could contribute to the greater NE release: 1) increased sympathetic nerve discharge and 2) increased NE in the neurovascular junction for a given level of sympathetic discharge. In this report, we focus on the second of these two general issues and test the following hypotheses: 1) in HF for a given level of sympathetic nerve stimulation, NE concentration in the interstitium (an index of neurovascular NE) would be greater, and 2) the greater interstitial NE concentration would be linked to reduced NE uptake. Studies were performed in rats 8-10 wk after induction of myocardial infarction (MI). Interstitial NE samples were collected from microdialysis probes inserted into the hindlimb muscle. Dialysate concentration of NE was determined by the HPLC method. First, interstitial NE concentration increased during electrical stimulation of the lumbar sympathetic nerves in eight control rats. An increase in interstitial NE concentration was significantly greater in 10 rats with severe MI. Additionally, an NE uptake-1 inhibitor (desipramine, 1 microM) was injected into the arterial blood supply of the muscle in six control and eight MI rats. Desipramine increased interstitial NE concentration by 24% in control and by only 3% (P < 0.05 vs. control) in MI rats. In conclusion, given levels of electrical stimulation of the lumbar sympathetic nerve lead to higher interstitial NE concentration in HF. This effect is due, in part, to reduced NE uptake-1 in HF.
Xing
Jihong
J
Penn State Heart and Vascular Institute, The Pennsylvania State University College of Medicine, Milton S. Hershey Medical Center, 500 Univ. Dr., Hershey, PA 17033, USA.
Koba
Satoshi
S
Kehoe
Valerie
V
Gao
Zhaohui
Z
Rice
Kristen
K
King
Nicholas
N
Sinoway
Lawrence
L
Li
Jianhua
J
D018759:Adrenergic Uptake Inhibitors / Q000494:pharmacology; D000818:Animals; D002303:Cardiac Output, Low / Q000209:etiology / Q000378:metabolism* / Q000503:physiopathology; D002851:Chromatography, High Pressure Liquid; D003331:Coronary Vessels / Q000601:surgery; D003891:Desipramine / Q000494:pharmacology; D004195:Disease Models, Animal; D004558:Electric Stimulation / Q000379:methods; D045604:Extracellular Fluid / Q000378:metabolism*; D006614:Hindlimb; D008026:Ligation; D008160:Lumbosacral Plexus / Q000378:metabolism; D008297:Male; D017551:Microdialysis; D018482:Muscle, Skeletal / Q000187:drug effects / Q000294:innervation / Q000378:metabolism*; D009203:Myocardial Infarction / Q000150:complications* / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology; D017202:Myocardial Ischemia / Q000150:complications* / Q000378:metabolism / Q000503:physiopathology; D009638:Norepinephrine / Q000378:metabolism*; D050484:Norepinephrine Plasma Membrane Transport Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012720:Severity of Illness Index; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D016277:Ventricular Function, Left
D018759:Adrenergic Uptake Inhibitors; D050484:Norepinephrine Plasma Membrane Transport Proteins; C493226:Slc6a2 protein, rat; D003891:Desipramine; D009638:Norepinephrine