Plasma nitrate accumulation during the development of pacing-induced dilated cardiac myopathy in conscious dogs is due to renal impairment.
Heart failure is associated with an increase in plasma nitrate and nitrite (NOx). To date there is still some controversy regarding the causes of nitrate accumulation during the development of heart failure. The goal of this study was to analyze the underlying mechanisms that cause accumulation of plasma nitrates during the development of heart failure in dogs. Dogs were chronically instrumented for measurement of hemodynamics and renal function. Hearts were paced initially at 210 bpm for 3 weeks and then at 240 until the development of heart failure. Hemodynamics, renal function, renal blood flow, arterial blood gases, hemoglobin, plasma and urine NOx levels, and creatinine levels were measured weekly. Heart failure was assessed by hemodynamic alterations, physical signs such as lethargy, ascites, cachexia, and postmortem evidence of cardiac hypertrophy. LVSP (from 127 +/- 3 to 106 +/- 3 mmHg), LV dP/dt (from 2658 +/- 173 to 1439 +/- 217 mmHg/s), MAP (from 101 +/- 1.9 to 83 +/- 1.8 mmHg) fell, whereas LVEDP tripled (from 6.4 +/- 0.9 to 20 +/- 2.6 mmHg), and heart rate rose (from 101 +/- 4.2 to 117 +/- 6.3 bpm), all changes P < 0.05. RBF (from 146 +/- 10 to 96 +/- 9.9 ml/min), urine output (V) (from 0.26 +/- 0.02 to 0.16 +/- 0.02 ml/min), GFR (from 63 +/- 1.8 to 49 +/- 2 ml/min), and Na excretion (from 45 +/- 4.5 to 14 +/- 4.6 microEq/min) all decreased (P < 0.05), whereas RVR increased (from 0.68 +/- 0.05 to 0.94 +/- 0.1 mmHg/ml/min). These changes took place during a rise in plasma NOx (from 3.7 +/- 0.5 to 16+/-3.3 microM), a decrease in urine NOx (from 33 +/- 9.9 to 8.1 +/- 4.9 microM), and a concurrent increase in NOx reabsorption (from 221 +/- 31 to 818 +/- 166 nmol/min). There was a direct correlation between the increase in plasma NOx levels and an increase in filtered load (r(2) = 0.97, P = 0.02), a negative correlation between NOx levels and NOx excretion (r(2) = 0.65 P < 0.09), and a direct correlation between plasma NOx levels and NOx reabsorption (r(2) = 0.97, P = 0.02). These results indicate that elevated plasma NOx during heart failure are most likely the result of an impairment of the renal function and not increased NOx production. Furthermore, without knowing changes in renal function the measurement of plasma NOx in and of itself is a meaningless index of NO formation.
Osorio
J C
JC
Department of Physiology, New York Medical College, Valhalla, New York 10595, USA.
Xu
X
X
Vogel
T
T
Ochoa
M
M
Laycock
S
S
Hintze
T H
TH
D000818:Animals; D001201:Ascites / Q000209:etiology; D002100:Cachexia / Q000209:etiology; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects; D002311:Cardiomyopathy, Dilated / Q000097:blood* / Q000209:etiology / Q000652:urine; D003243:Consciousness; D003404:Creatinine / Q000097:blood / Q000652:urine; D004285:Dogs; D005260:Female; D005919:Glomerular Filtration Rate; D006333:Heart Failure / Q000097:blood / Q000209:etiology / Q000652:urine; D006439:Hemodynamics; D007668:Kidney / Q000503:physiopathology; D009318:Natriuresis; D009566:Nitrates / Q000097:blood* / Q000652:urine; D009569:Nitric Oxide / Q000378:metabolism; D009573:Nitrites / Q000097:blood* / Q000652:urine; D010100:Oxygen / Q000097:blood; D010108:Oxyhemoglobins / Q000032:analysis; D010313:Partial Pressure; D012079:Renal Circulation
D009566:Nitrates; D009573:Nitrites; D010108:Oxyhemoglobins; D009569:Nitric Oxide; D003404:Creatinine; D010100:Oxygen